Added tasks 39-72

Author: javadev

README.md

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+[![](https://img.shields.io/github/stars/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript)
+[![](https://img.shields.io/github/forks/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript/fork)
+
+## 39\. Combination Sum
+
+Medium
+
+Given an array of **distinct** integers `candidates` and a target integer `target`, return _a list of all **unique combinations** of_ `candidates` _where the chosen numbers sum to_ `target`_._ You may return the combinations in **any order**.
+
+The **same** number may be chosen from `candidates` an **unlimited number of times**. Two combinations are unique if the frequency of at least one of the chosen numbers is different.
+
+It is **guaranteed** that the number of unique combinations that sum up to `target` is less than `150` combinations for the given input.
+
+**Example 1:**
+
+**Input:** candidates = [2,3,6,7], target = 7
+
+**Output:** [[2,2,3],[7]]
+
+**Explanation:**
+
+    2 and 3 are candidates, and 2 + 2 + 3 = 7. Note that 2 can be used multiple times.
+    7 is a candidate, and 7 = 7.
+    These are the only two combinations. 
+
+**Example 2:**
+
+**Input:** candidates = [2,3,5], target = 8
+
+**Output:** [[2,2,2,2],[2,3,3],[3,5]] 
+
+**Example 3:**
+
+**Input:** candidates = [2], target = 1
+
+**Output:** [] 
+
+**Example 4:**
+
+**Input:** candidates = [1], target = 1
+
+**Output:** [[1]] 
+
+**Example 5:**
+
+**Input:** candidates = [1], target = 2
+
+**Output:** [[1,1]] 
+
+**Constraints:**
+
+*   `1 <= candidates.length <= 30`
+*   `1 <= candidates[i] <= 200`
+*   All elements of `candidates` are **distinct**.
+*   `1 <= target <= 500`
+
+## Solution
+
+```typescript
+function combinationSum(candidates: number[], target: number): number[][] {
+    const result: number[][] = []
+    const path: number[] = []
+
+    const comFunct = (index: number, sum: number) => {
+        if (sum === target) {
+            result.push([...path])
+            return
+        }
+        if (sum > target) return
+        for (let i = index; i < candidates.length; i++) {
+            path.push(candidates[i])
+            comFunct(i, sum + candidates[i])
+            path.pop()
+        }
+    }
+    comFunct(0, 0)
+    return result
+}
+
+export { combinationSum }
+```

src/main/ts/g0001_0100/s0039_combination_sum/readme.md

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+[![](https://img.shields.io/github/stars/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript)
+[![](https://img.shields.io/github/forks/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript/fork)
+
+## 41\. First Missing Positive
+
+Hard
+
+Given an unsorted integer array `nums`, return the smallest missing positive integer.
+
+You must implement an algorithm that runs in `O(n)` time and uses constant extra space.
+
+**Example 1:**
+
+**Input:** nums = [1,2,0]
+
+**Output:** 3 
+
+**Example 2:**
+
+**Input:** nums = [3,4,-1,1]
+
+**Output:** 2 
+
+**Example 3:**
+
+**Input:** nums = [7,8,9,11,12]
+
+**Output:** 1 
+
+**Constraints:**
+
+*   <code>1 <= nums.length <= 5 * 10<sup>5</sup></code>
+*   <code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code>
+
+## Solution
+
+```typescript
+function firstMissingPositive(nums: number[]): number {
+    let i = 0
+    while (i < nums.length) {
+        let correctIndex = nums[i] - 1
+        if (nums[i] > 0 && nums[i] <= nums.length && nums[i] !== nums[correctIndex]) {
+            ;[nums[i], nums[correctIndex]] = [nums[correctIndex], nums[i]]
+        } else {
+            i++
+        }
+    }
+    for (let i = 0; i < nums.length; i++) {
+        if (nums[i] !== i + 1) {
+            return i + 1
+        }
+    }
+    return nums.length + 1
+}
+
+export { firstMissingPositive }
+```

src/main/ts/g0001_0100/s0041_first_missing_positive/readme.md

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+[![](https://img.shields.io/github/stars/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript)
+[![](https://img.shields.io/github/forks/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript/fork)
+
+## 42\. Trapping Rain Water
+
+Hard
+
+Given `n` non-negative integers representing an elevation map where the width of each bar is `1`, compute how much water it can trap after raining.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2018/10/22/rainwatertrap.png)
+
+**Input:** height = [0,1,0,2,1,0,1,3,2,1,2,1]
+
+**Output:** 6
+
+**Explanation:** The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped. 
+
+**Example 2:**
+
+**Input:** height = [4,2,0,3,2,5]
+
+**Output:** 9 
+
+**Constraints:**
+
+*   `n == height.length`
+*   <code>1 <= n <= 2 * 10<sup>4</sup></code>
+*   <code>0 <= height[i] <= 10<sup>5</sup></code>
+
+## Solution
+
+```typescript
+function trap(height: number[]): number {
+    let result = 0
+    let left = 1
+    let right = height.length - 2
+    let leftMax = height[left - 1]
+    let rightMax = height[right + 1]
+    while (left <= right) {
+        if (leftMax < rightMax) {
+            leftMax = Math.max(leftMax, height[left])
+            result += leftMax - height[left]
+            left++
+        } else {
+            rightMax = Math.max(rightMax, height[right])
+            result += rightMax - height[right]
+            right--
+        }
+    }
+    return result
+}
+
+export { trap }
+```

src/main/ts/g0001_0100/s0042_trapping_rain_water/readme.md

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+[![](https://img.shields.io/github/stars/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript)
+[![](https://img.shields.io/github/forks/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript/fork)
+
+## 45\. Jump Game II
+
+Medium
+
+Given an array of non-negative integers `nums`, you are initially positioned at the first index of the array.
+
+Each element in the array represents your maximum jump length at that position.
+
+Your goal is to reach the last index in the minimum number of jumps.
+
+You can assume that you can always reach the last index.
+
+**Example 1:**
+
+**Input:** nums = [2,3,1,1,4]
+
+**Output:** 2
+
+**Explanation:** The minimum number of jumps to reach the last index is 2. Jump 1 step from index 0 to 1, then 3 steps to the last index. 
+
+**Example 2:**
+
+**Input:** nums = [2,3,0,1,4]
+
+**Output:** 2 
+
+**Constraints:**
+
+*   <code>1 <= nums.length <= 10<sup>4</sup></code>
+*   `0 <= nums[i] <= 1000`
+
+## Solution
+
+```typescript
+function jump(nums: number[]): number { //NOSONAR
+    let minJmp = new Array(nums.length)
+    if (nums.length === 1) return 0
+    let prevIndex = 0
+    minJmp[prevIndex] = 0
+    while (prevIndex < nums.length - 1) {
+        let nextMaxJmpTo = nums[prevIndex] + prevIndex
+        let prevIndexJmp = minJmp[prevIndex]
+
+        let farthestJumpVal = -1
+        let farthestJumpIndex = -1
+        for (let i = nextMaxJmpTo; ; i--) {
+            if (i >= nums.length) {
+                continue
+            }
+            if (i === nums.length - 1) {
+                return prevIndexJmp + 1
+            }
+            if (minJmp[i] != undefined) {
+                break
+            }
+            minJmp[i] = prevIndexJmp + 1
+            let curmaxTo = nums[i] + i
+            if (farthestJumpVal < curmaxTo) {
+                farthestJumpVal = curmaxTo
+                farthestJumpIndex = i
+            }
+        }
+        if (farthestJumpIndex === -1) {
+            return -1
+        }
+        prevIndex = farthestJumpIndex
+    }
+    return minJmp[nums.length - 1]
+}
+
+export { jump }
+```

src/main/ts/g0001_0100/s0045_jump_game_ii/readme.md

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+[![](https://img.shields.io/github/stars/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript)
+[![](https://img.shields.io/github/forks/LeetCode-in-TypeScript/LeetCode-in-TypeScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-TypeScript/LeetCode-in-TypeScript/fork)
+
+## 46\. Permutations
+
+Medium
+
+Given an array `nums` of distinct integers, return _all the possible permutations_. You can return the answer in **any order**.
+
+**Example 1:**
+
+**Input:** nums = [1,2,3]
+
+**Output:** [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] 
+
+**Example 2:**
+
+**Input:** nums = [0,1]
+
+**Output:** [[0,1],[1,0]] 
+
+**Example 3:**
+
+**Input:** nums = [1]
+
+**Output:** [[1]] 
+
+**Constraints:**
+
+*   `1 <= nums.length <= 6`
+*   `-10 <= nums[i] <= 10`
+*   All the integers of `nums` are **unique**.
+
+## Solution
+
+```typescript
+function permute(nums: number[]): number[][] {
+    const result: number[][] = []
+    const permuteRecursive = (nums: number[], index: number, result: number[][]) => {
+        if (index >= nums.length) {
+            result.push([...nums])
+        }
+        for (let i = index; i < nums.length; i++) {
+            ;[nums[index], nums[i]] = [nums[i], nums[index]]
+            permuteRecursive(nums, index + 1, result)
+            ;[nums[index], nums[i]] = [nums[i], nums[index]]
+        }
+    }
+    permuteRecursive(nums, 0, result)
+    return result
+}
+
+export { permute }
+```