next_permutation(start, end)

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

void printV(vector<int> &v){
    for(int i = 0; i < v.size(); i++) {
        cout << v[i] << " ";
    }
    cout << '\\n';
}

int cnt = 0;
int main(){
    for(int i = 1; i <= 3; i++) v.push_back(i);
    do{
        printV(v);
        cnt += 1;
    }while(next_permutation(v.begin(), v.end()));
    cout << cnt << '\\n';
    return 0;
}

// 출력
1 2 3 
1 3 2 
2 1 3 
2 3 1 
3 1 2 
3 2 1
6

재귀함수

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

void printV(vector<int> &v){
    for(int i = 0; i < v.size(); i++) {
        cout << v[i] << " ";
    }
    cout << '\\n';
}

void makePermutation(int n, int r, int depth){
    if(r == depth){
        printV(v);
        // logic
        return;
    }
    for(int i = depth; i < n; i++){
        swap(v[i], v[depth]);
        makePermutation(n, r, depth+1);
        swap(v[i], v[depth]);
    }
    return;
}

int main(){
    for(int i = 0; i <= 3; i++)v.push_back(i); makePermutation(3, 3, 0);
    return 0;
}