next permutation

next_perm

#include <algorithm>
class Solution {
public:
    void nextPermutation(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int>::iterator  first, last,i , j , k;
        (); ();
        if(first==last) return;
        ; i++;
        if(i==last) return ;
        ; i--;
       
        for(;;){
            ;
            --i;
            if(*i<*k){
                ;
                while(!(*i<*--j)) ;
                std::iter_swap(i,j); 
                std::reverse(k,last);
                return ;
            }
            if(i==first){
                std::reverse(first, last);
                return;
            }
        }
    }
};