LeetCode-31. Next Permutation

LeetCode-31. Next Permutation

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

The replacement must be ​​in-place​​

Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.

​​1,2,3​​​ → ​​1,3,2​​​​3,2,1​​ → ​​1,2,3​​​​1,1,5​​ → ​​1,5,1​​

​​题解：​​

从后往前找，找到第一个逆序对，即nums[p + 1] < nums[p]，然后再次从后往前找，找到第一个比p大的数下标q，交换nums[p]和nums[q]，之后再把p后面的元素升序排列获取最小值。

class Solution {public: void swap(int &a, int &b) { int idx = a; a = b; b = idx; } void nextPermutation(vector& nums) { int n = nums.size(); if (n <= 1) { return; } int p = n - 2; while (p >= 0 && nums[p] >= nums[p + 1]) { p--; } int q = n - 1; if (p >= 0) { while (q > p && nums[q] <= nums[p]) { q--; } swap(nums[p], nums[q]); } sort(nums.begin() + p + 1, nums.end()); }};

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