1class Solution {2    public void nextPermutation(int[] nums) {3        int i = nums.length - 2;4        while (i >= 0 && nums[i] >= nums[i + 1]) i--;5        if (i >= 0) {6            int j = nums.length - 1;7            while (nums[j] <= nums[i]) j--;8            swap(nums, i, j);9        }10        int left = i + 1, right = nums.length - 1;11        while (left < right) {12            swap(nums, left++, right--);13        }14    }15    private void swap(int[] nums, int a, int b) {16        int temp = nums[a];17        nums[a] = nums[b];18        nums[b] = temp;19    }20}