rename the directory & add shell problems

Author: haoel

README.md

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+# Source : https://leetcode.com/problems/tenth-line/
+# Author : Hao Chen
+# Date   : 2015-03-31
+
+################################################################################## 
+# 
+# How would you print just the 10th line of a file?
+# 
+# For example, assume that file.txt has the following content:
+# 
+# Line 1
+# Line 2
+# Line 3
+# Line 4
+# Line 5
+# Line 6
+# Line 7
+# Line 8
+# Line 9
+# Line 10
+# 
+# Your script should output the tenth line, which is:
+# 
+# Line 10
+# 
+# [show hint]
+# Hint:
+# 1. If the file contains less than 10 lines, what should you output?
+# 2. There's at least three different solutions. Try to explore all possibilities.
+##################################################################################
+
+#!/bin/sh
+
+
+# Read from the file file.txt and output the tenth line to stdout.
+
+# Solution One
+awk 'NR==10{print $0}' file.txt
+
+# Solution Two
+sed -n '10p' file.txt
+

src/3Sum/3Sum.cpp algorithms/3Sum/3Sum.cpp

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+# Source : https://leetcode.com/problems/transpose-file/
+# Author : Hao Chen
+# Date   : 2015-03-31
+
+################################################################################## 
+# 
+# Given a text file file.txt, transpose its content.
+# 
+# You may assume that each row has the same number of columns and each field is separated by the ' ' character.
+# 
+# For example, if file.txt has the following content:
+# 
+# name age
+# alice 21
+# ryan 30
+# 
+# Output the following:
+# 
+# name alice ryan
+# age 21 30
+##################################################################################
+
+#!/bin/sh
+
+# Read from the file file.txt and print its transposed content to stdout.
+awk '
+{
+    for (i = 1; i <= NF; i++) {
+        if (NR == 1){
+            s[i]=$i;
+        }else{
+            s[i] = s[i] " " $i;
+        }
+    }
+}
+END {
+    for (i = 1; s[i] != ""; i++) {
+        print s[i];
+    }
+}' file.txt
+
+
+

src/3SumClosest/3SumClosest.cpp algorithms/3SumClosest/3SumClosest.cpp

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+# Source : https://leetcode.com/problems/valid-phone-numbers/
+# Author : Hao Chen
+# Date   : 2015-03-31
+
+################################################################################## 
+# 
+# Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.
+# 
+# You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)
+# 
+# You may also assume each line in the text file must not contain leading or trailing white spaces.
+# 
+# For example, assume that file.txt has the following content:
+# 
+# 987-123-4567
+# 123 456 7890
+# (123) 456-7890
+# 
+# Your script should output the following valid phone numbers:
+# 
+# 987-123-4567
+# (123) 456-7890
+##################################################################################
+
+#!/bin/sh
+
+
+# Read from the file file.txt and output all valid phone numbers to stdout.
+grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt
+

src/4Sum/4Sum.cpp algorithms/4Sum/4Sum.cpp

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+# Source : https://leetcode.com/problems/word-frequency/
+# Author : Hao Chen
+# Date   : 2015-03-31
+
+################################################################################## 
+# 
+# Write a bash script to calculate the frequency of each word in a text file words.txt.
+# 
+# For simplicity sake, you may assume:
+# 
+# words.txt contains only lowercase characters and space ' ' characters.
+# Each word must consist of lowercase characters only.
+# Words are separated by one or more whitespace characters.
+# 
+# For example, assume that words.txt has the following content:
+# the day is sunny the the
+# the sunny is is
+# 
+# Your script should output the following, sorted by descending frequency:
+# 
+# the 4
+# is 3
+# sunny 2
+# day 1
+# 
+# Note:
+# Don't worry about handling ties, it is guaranteed that each word's frequency count is unique.
+# 
+# [show hint]
+# Hint:
+# Could you write it in one-line using Unix pipes?
+##################################################################################
+
+#!/bin/sh
+
+# Read from the file words.txt and output the word frequency list to stdout.
+cat words.txt | tr [:space:] "\n" | sed '/^$/d' | tr '[:upper:]' '[:lower:]'|sort|uniq -c|sort -nr | awk '{ print $2,$1}'
+