NextPermutation.cpp

#include<bits/stdc++.h>
using namespace std;

 void nextPermutation(vector<int>& nums) {
        int index = -1;
        int n = nums.size();
        
        for(int i=n-1; i>0;i--){
            if(nums[i]>nums[i-1]){
                index= i;
                break;
            }
        }
        if(index==-1)
            reverse(nums.begin(), nums.end());
        else{
            int prev =index;
            for(int i= index+1; i<n;i++){
                if(nums[i]>nums[index-1] && nums[i]<=nums[prev]){
                    prev=i;
                }
            }
            swap(nums[index-1], nums[prev]);
            reverse(nums.begin()+index, nums.end());
        }
    }

int main(){
    int n;
    cin>>n;
    vector <int> nums;
    for(int i=0; i<n; i++){
        nums.push_back(n);
    }
    nextPermutation(nums);
    return 0;
}