update: 31

Author: hijiangtao

README.md

@@ -31,6 +31,7 @@ This is the solutions collection of my LeetCode submissions, most of them are pr
 | 27  | [Remove Element](https://leetcode.com/problems/remove-element/)                                                                                 | [JavaScript](./src/remove-element/res.js)                                                                             | Easy       |
 | 28  | [Implement strStr()](https://leetcode.com/problems/implement-strstr/)                                                                           | [JavaScript](./src/implement-strstr/res.js)                                                                           | Easy       |
 | 29  | [Divide Two Integers](https://leetcode.com/problems/divide-two-integers/)                                                                       | [JavaScript](./src/divide-two-integers/res.js)                                                                        | Medium     |
+| 31  | [next-permutation](https://leetcode.com/problems/next-permutation/)                                                                             | [TypeScript](./src/next-permutation/res.ts)                                                                           | Medium     |
 | 33  | [Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/)                                                 | [JavaScript](./src/search-in-rotated-sorted-array/res.js)                                                             | Medium     |
 | 34  | [Search for a Range](https://leetcode.com/problems/search-for-a-range/)                                                                         | [JavaScript](./src/search-for-a-range/res.js)                                                                         | Medium     |
 | 35  | [Search Insert Position](https://leetcode.com/problems/search-insert-position/)                                                                 | [JavaScript](./src/search-insert-position/res.js)                                                                     | Easy       |

src/next-permutation/res.ts

@@ -0,0 +1,47 @@
+/**
+ Do not return anything, modify nums in-place instead.
+ */
+function nextPermutation(nums: number[]): void {
+    let currentPointer = nums.length - 1;
+    let mutationCount = 0;
+
+    if (currentPointer < 1) {
+        return ;
+    }
+
+    while (!mutationCount || currentPointer <= nums.length-1 && currentPointer > 0) {
+        mutationCount++;
+        if (currentPointer > 0 && nums[currentPointer] > nums[currentPointer-1]) {
+            currentPointer--;
+            break;
+        }
+
+        currentPointer--;
+    }
+
+    let swapPointer = nums.length-1;
+    while(swapPointer > 0 && nums[swapPointer] <= nums[currentPointer]) {
+        swapPointer--;
+    }
+
+    if (!currentPointer && !swapPointer) {
+        nums.sort((a, b) => a - b);
+    } else if (currentPointer === nums.length-2) {
+        const swapPointer = currentPointer+1;
+        const swapValue = nums[swapPointer];
+        nums[swapPointer] = nums[currentPointer];
+        nums[currentPointer] = swapValue;
+    } else {
+        // swap
+        const swapValue = nums[swapPointer];
+        nums[swapPointer] = nums[currentPointer];
+        nums[currentPointer] = swapValue;
+
+        const restList = nums.slice(currentPointer + 1);
+        restList.sort((a, b) => a - b);
+
+        for (let j = currentPointer + 1; j < nums.length; j++) {
+            nums[j] = restList[j-currentPointer-1];
+        }
+    }
+};