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‎ExcelSheetColumnTitle/excel_sheet_column_title.dart

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/*
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-* Excel Sheet Column Title *-
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Given an integer columnNumber, return its corresponding
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column title as it appears in an
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Excel sheet.
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For example:
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A -> 1
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B -> 2
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C -> 3
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...
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Z -> 26
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AA -> 27
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AB -> 28
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...
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Example 1:
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Input: columnNumber = 1
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Output: "A"
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Example 2:
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Input: columnNumber = 28
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Output: "AB"
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Example 3:
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Input: columnNumber = 701
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Output: "ZY"
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Constraints:
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1 <= columnNumber <= 231 - 1
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*/
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class A {
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/**
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* Time Complexity: O(log26n), as we are using a loop and in each traversal, we decrement by floor division of 26.
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Auxiliary Space: O(10000), as we are using extra space for the array.
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*/
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// Runtime: 512 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 141.5 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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List<int> arr = List.filled(10000, 0);
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int i = 0;
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// Step 1: Converting to number assuming
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// 0 in number system
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while (columnNumber > 0) {
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arr[i] = columnNumber % 26;
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columnNumber = columnNumber ~/ 26;
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i++;
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}
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// Step 2: Getting rid of 0, as 0 is
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// not part of number system
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for (int j = 0; j < i - 1; j++) {
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if (arr[j] <= 0) {
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arr[j] += 26;
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arr[j + 1] = arr[j + 1] - 1;
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}
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}
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String ans = '';
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for (int j = i; j >= 0; j--) {
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if (arr[j] > 0) ans += String.fromCharCode(65 + arr[j] - 1);
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}
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return ans;
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}
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}
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class B {
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// Runtime: 391 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 140.1 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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String alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
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if (columnNumber < 26)
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return alpha[columnNumber - 1];
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else {
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int q = (columnNumber ~/ 26), r = columnNumber % 26;
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if (r == 0) {
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if (q == 1)
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return alpha[(26 + r - 1)];
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else
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return convertToTitle(q - 1) + alpha[(26 + r - 1)];
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} else
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return convertToTitle(q) + alpha[r - 1];
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}
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}
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}
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class C {
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// Runtime: 490 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 150.5 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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if (columnNumber-- == 0) return "";
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return convertToTitle(columnNumber ~/ 26) +
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String.fromCharCode((columnNumber % 26) + 'A'.codeUnitAt(0));
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}
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}
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class D {
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// Runtime: 305 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 157.9 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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StringBuffer result = StringBuffer();
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while (columnNumber > 0) {
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columnNumber--;
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//result.write(0, ('A' + n % 26));
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result.writeCharCode(((columnNumber % 26) + 'A'.codeUnitAt(0)));
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columnNumber ~/= 26;
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}
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return result.toString().split("").reversed.join("");
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}
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}
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class E {
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// Runtime: 324 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 140 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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return columnNumber == 0
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? ""
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: convertToTitle(--columnNumber ~/ 26) +
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String.fromCharCode((columnNumber % 26) + 'A'.codeUnitAt(0));
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}
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}

‎ExcelSheetColumnTitle/excel_sheet_column_title.go

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package main
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import "fmt"
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// func convertToTitle(n int) string {
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// result := ""
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// for n != 0 {
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// fmt.Println(n)
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// result = string('A'+(n-1)%26) + result
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// n = (n - 1) / 26
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// }
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// return result
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// }
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func convertToTitle(n int) string {
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result := ""
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for n != 0 {
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fmt.Println(n)
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result = string(rune('A'+(n-1)%26)) + result
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n = (n - 1) / 26
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}
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return result
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}

‎ExcelSheetColumnTitle/excel_sheet_column_title.md

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# 🔥 Find K Closest Elements 🔥 || 5 Solutions || Simple Fast and Easy || with Explanation
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## Solution - 1
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The problem is similar to converting a decimal number to its binary representation but instead of a binary base system where we have two digits only 0 and 1, here we have 26 characters from A-Z.
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So, we are dealing with base 26 instead of base binary.
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That’s not where the fun ends, we don’t have zero in this number system, as A represents 1, B represents 2 and so on Z represents 26.
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To make the problem easily understandable, we approach the problem in two steps:
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Convert the number to base 26 representation, considering we have 0 also in the system.
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Change the representation to the one without having 0 in its system.
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HOW? Here is an example
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Step 1:
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Consider we have number 676, How to get its representation in the base 26 system? In the same way, we do for a binary system, Instead of division and remainder by 2, we do division and remainder by 26.
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Base 26 representation of 676 is : 100
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Step2
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But Hey, we can’t have zero in our representation. Right? Because it’s not part of our number system. How do we get rid of zero? Well it’s simple, but before doing that let’s remind one simple math trick:
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Subtraction:
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5000 - 9, How do you subtract 9 from 0 ? You borrow
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from next significant bit, right.
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In a decimal number system to deal with zero, we borrow 10 and subtract 1 from the next significant.
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In the Base 26 Number System to deal with zero, we borrow 26 and subtract 1 from the next significant bit.
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So Convert 10026 to a number system that does not have ‘0’, we get (25 26)26
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Symbolic representation of the same is: YZ
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* Time Complexity: O(log26n), as we are using a loop and in each traversal, we decrement by floor division of 26.
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* Auxiliary Space: O(10000), as we are using extra space for the array.
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```dart
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class Solution {
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// Runtime: 512 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 141.5 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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List<int> arr = List.filled(10000, 0);
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int i = 0;
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// Step 1: Converting to number assuming
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// 0 in number system
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while (columnNumber > 0) {
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arr[i] = columnNumber % 26;
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columnNumber = columnNumber ~/ 26;
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i++;
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}
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// Step 2: Getting rid of 0, as 0 is
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// not part of number system
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for (int j = 0; j < i - 1; j++) {
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if (arr[j] <= 0) {
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arr[j] += 26;
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arr[j + 1] = arr[j + 1] - 1;
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}
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}
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String ans = '';
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for (int j = i; j >= 0; j--) {
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if (arr[j] > 0) ans += String.fromCharCode(65 + arr[j] - 1);
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}
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return ans;
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}
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}
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```
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## Solution - 2
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We can use a recursive function which definitely reduces the time and increase the efficiency:
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Alphabets are in sequential order like: ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’. You have experienced while using excel when you see columns and rows numbering are done in Alphabetical ways.
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Here’s How I purposefully think about the logic of how it is arranged.
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(In Mathematical terms, [a , b ] means from ‘a’ to ‘b’).
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[1,26] = [A,Z] (Understand by ‘1’ stands for ‘A’ and ’26” stands for “Z”). For [27,52] ,it will be like [AA,AZ], For [57,78] it will be [BA,BZ]
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Logic is to append an Alphabet sequentially whenever it ends up numbering at 26.
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For example, if the number is ’27’ which is greater than ’26’, then we simply need to divide by 26, and we get the remainder as 1, We see “1” as “A” and can be recursively done.
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we will be using python for this.
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Algorithm is:
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1. Take an array and Sort the letters from A to Z . (You can also use the import string and string function to get “A to Z” in uppercase.)
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2. If the number is less than or equal to ’26’, simply get the letter from the array and print it.
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3. If it is greater than 26, use the Quotient Remainder rule, if the remainder is zero, there are 2 possible ways, if the quotient is “1”, simply hash out the letter from the index [r-1]( ‘r’ is remainder), else call out the function from the num =(q-1) and append at the front to the letter indexing [r-1].
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4. If the remainder is not equal to “0”, call the function for the num = (q) and append at the front to the letter indexing [r-1].
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Time Complexity: O(log26n), as we are using recursion and in each recursive call, we decrement by floor division of 26.
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Auxiliary Space: O(1), as we are not using any extra space.
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```dart
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class Solution {
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// Runtime: 391 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 140.1 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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String alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
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if (columnNumber < 26)
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return alpha[columnNumber - 1];
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else {
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int q = (columnNumber ~/ 26), r = columnNumber % 26;
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if (r == 0) {
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if (q == 1)
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return alpha[(26 + r - 1)];
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else
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return convertToTitle(q - 1) + alpha[(26 + r - 1)];
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} else
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return convertToTitle(q) + alpha[r - 1];
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}
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}
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}
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```
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## Solution - 3
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```dart
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class Solution {
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// Runtime: 490 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 150.5 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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if (columnNumber-- == 0) return "";
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return convertToTitle(columnNumber ~/ 26) +
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String.fromCharCode((columnNumber % 26) + 'A'.codeUnitAt(0));
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}
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}
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```
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## Solution - 4
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```dart
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class Solution {
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// Runtime: 305 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 157.9 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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StringBuffer result = StringBuffer();
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while (columnNumber > 0) {
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columnNumber--;
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result.writeCharCode(((columnNumber % 26) + 'A'.codeUnitAt(0)));
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columnNumber ~/= 26;
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}
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return result.toString().split("").reversed.join("");
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}
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}
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```
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## Solution - 5
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```dart
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class Solution {
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// Runtime: 324 ms, faster than 50.00% of Dart online submissions for Excel Sheet Column Title.
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// Memory Usage: 140 MB, less than 50.00% of Dart online submissions for Excel Sheet Column Title.
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String convertToTitle(int columnNumber) {
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return columnNumber == 0
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? ""
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: convertToTitle(--columnNumber ~/ 26) +
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String.fromCharCode((columnNumber % 26) + 'A'.codeUnitAt(0));
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}
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}
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```

‎README.md

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- [Intersection of Two Linked Lists](IntersectionOfTwoLinkedLists/intersection_of_two_linked_lists.dart)
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- [Missing Ranges](MissingRanges/missing_ranges.dart)
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- [Find K Closest Elements](FindKClosestElements/find_k_closest_elements.dart)
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- [Excel Sheet Column Title](ExcelSheetColumnTitle/excel_sheet_column_title.dart)
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## Reach me via
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