LetCode 31. 下一个排列

static int x=[](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    void nextPermutation(vector<int>& nums) {
        if (nums.size() <= 1)
            return;
        int left = 0;
        bool flag = false;
        for (int i = nums.size() - 2; i >= 0; i--)
            if (nums[i] < nums[i + 1]){
                if (i == nums.size() - 2){
                    int temp = nums[i];        
                    nums[i] = nums[i + 1];
                    nums[i + 1] = temp;
                }else{                    
                    for (int j = i + 1; j < nums.size(); j++){
                        if (nums[j] <= nums[i]){
                            int temp = nums[i];
                            nums[i] = nums[j - 1];
                            nums[j - 1] = temp;
                            break;
                        }
                        if (j == nums.size() - 1){
                            int temp = nums[i];
                            nums[i] = nums[j];
                            nums[j] = temp;
                        }
                    }
                    sort(nums.begin() + i + 1, nums.end());
                }
                flag = true;
                break;
            }
        if (!flag)
            sort(nums.begin(), nums.end());
    }
};