力扣第31题-下一个排序

题目
题目链接

题解

class Solution {
    
    public void nextPermutation(int[] nums) {
        if (nums == null) {
            return;
        }
        int n = nums.length;
        if (n == 1 || n == 0) {
            return;
        }
        for (int i = n - 2; i >= 0; i--) {
            if (nums[i] < nums[i + 1]) {
                for (int j = n - 1; j > i; j--) {
                    if (nums[i] < nums[j]) {
                        int temp = nums[i];
                        nums[i] = nums[j];
                        nums[j] = temp;
                        break;
                    }
                }
                reverse(nums, i + 1, n - 1);
                break;
            } else if (i == 0) {
                reverse(nums, 0, n - 1);
            }
        }
    }

    private void reverse(int[] nums, int from, int to) {
        if (nums == null || nums.length <= 1 || from < 0 || from >= to || from > nums.length - 1 || to < 0 || to > nums.length - 1) {
            return;
        }
        for (int i = from, j = to; i < j; i++, j--) {
            int temp = nums[i];
            nums[i] = nums[j];
            nums[j] = temp;
        }
    }
}