leetcode Next Permutation

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

void swap(int &a, int &b){
int t = a;
a = b;
b = t;
}

void nextPermutation(vector<int> &num) {
int L = num.size();
if (L < 1)
return;
int k = 0;
for (int i = L-2; i >=0; i--){
for (int j = L-1; j >i;j--){
if (num[j] > num[i]){
swap(num[i], num[j]);
sort(num.begin()+i+1,num.end());
return;
}
}
}
for (int i = 0; i <= L / 2; i++)
swap(num[i], num[L-1 - i]);
}

int main(){
vector<int> num = { 1,3,2 };
nextPermutation(num);
for (int i = 0; i < num.size(); i++)
cout << num[i] << endl;
}