Add: Excercise 88. Merge Sorted Array

Author: andresmunozit

88-merge-sorted-array/README.md

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+# Merge Sorted Array
+
+## Description
+
+You are given two integer arrays `nums1` and `nums2`, sorted in **non-decreasing order**, and two integers `m` and `n`, representing the number of elements in `nums1` and `nums2` respectively.
+
+**Merge** `nums1` and `nums2` into a single array sorted in **non-decreasing order**.
+
+The final sorted array should not be returned by the function, but instead be **stored inside the array** `nums1`. To accommodate this, `nums1` has a length of `m + n`, where the first `m` elements denote the elements that should be merged, and the last `n` elements are set to `0` and should be ignored. `nums2` has a length of `n`.
+
+---
+
+## Examples
+
+### Example 1:
+
+**Input:**
+```
+nums1 = [1,2,3,0,0,0], m = 3
+nums2 = [2,5,6], n = 3
+```
+**Output:**
+```
+[1,2,2,3,5,6]
+```
+**Explanation:**
+The arrays we are merging are `[1,2,3]` and `[2,5,6]`.  
+The result of the merge is `[1,2,2,3,5,6]` with the underlined elements coming from `nums1`.
+
+---
+
+### Example 2:
+
+**Input:**
+```
+nums1 = [1], m = 1
+nums2 = [], n = 0
+```
+**Output:**
+```
+[1]
+```
+**Explanation:**
+The arrays we are merging are `[1]` and `[]`.  
+The result of the merge is `[1]`.
+
+---
+
+### Example 3:
+
+**Input:**
+```
+nums1 = [0], m = 0
+nums2 = [1], n = 1
+```
+**Output:**
+```
+[1]
+```
+**Explanation:**
+The arrays we are merging are `[]` and `[1]`.  
+The result of the merge is `[1]`.  
+
+**Note:** Because `m = 0`, there are no elements in `nums1`. The `0` is only there to ensure the merge result can fit in `nums1`.
+
+---
+
+## Constraints
+
+- `nums1.length == m + n`
+- `nums2.length == n`

88-merge-sorted-array/index.js

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+const assert = require('assert');
+
+/**
+ * @param {number[]} nums1
+ * @param {number} m
+ * @param {number[]} nums2
+ * @param {number} n
+ * @return {void} Do not return anything, modify nums1 in-place instead.
+ */
+var merge = function (nums1, m, nums2, n) {
+  // nums1 = [a, b, c, 0, 0, 0]
+  // nums2 = [d, e, f]
+  // Three pointers:
+  // r1 (reader) = right of the relevant part of the first array (3)
+  // r2 (reader) = right of the second array (3)
+  // w (writter) = it will write at the end of the first array (5)
+  let r1 = m - 1;
+  let r2 = n - 1;
+
+  for (let w = m + n - 1; w >= 0; w--) {
+    if (r1 >= 0 && r2 >= 0) {
+      nums1[w] = nums1[r1] > nums2[r2] ? nums1[r1--] : nums2[r2--];
+    } else if (r1 >= 0) {
+      nums1[w] = nums1[r1--];
+    } else if (r2 >= 0) {
+      nums1[w] = nums2[r2--];
+    }
+  }
+};
+
+function test(tt) {
+  tt.forEach(t => {
+    merge(t.nums1, t.m, t.nums2, t.n);
+    assert.deepStrictEqual(t.nums1, t.expected);
+  });
+}
+
+const tt = [
+  {
+    nums1: [1, 2, 3, 0, 0, 0],
+    m: 3,
+    nums2: [2, 5, 6],
+    n: 3,
+    expected: [1, 2, 2, 3, 5, 6],
+  },
+  {
+    nums1: [1],
+    m: 1,
+    nums2: [],
+    n: 0,
+    expected: [1],
+  },
+  {
+    nums1: [0],
+    m: 0,
+    nums2: [1],
+    n: 1,
+    expected: [1],
+  },
+]
+
+test(tt);

88-merge-sorted-array/package.json

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+{
+  "name": "88-merge-sorted-array",
+  "version": "1.0.0",
+  "description": "## Description",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js",
+    "debug": "NODE_OPTIONS=--inspect-brk node index.js"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}