C++ 全排列函数next_permutation

有时候要用到全排列 next_permutation 进行枚举

<algorithm>

　　std::next_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp)

　　std::next_permutation(BidirectionalIterator first, BidirectionalIterator last )

实例1：

　　字典序降序全排列

    int num[3] = {1,2,3};//升序
    do{
        cout << num[0] << " " << num[1] << " " << num[2] << endl;
    }while(next_permutation(num,num+3));

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

 实例2: 

　　字典序升序全排列

#include <iostream>
#include <algorithm>
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAXN = 100 + 1;
int n;
long long L[MAXN];
int main(){
    ios::sync_with_stdio(false);
    int num[3] = {3,2,1};//降序排列 
    do{
        cout << num[0] << " " << num[1] << " " << num[2] << endl;
    }while(next_permutation(num,num+3,greater<int>()));
    
    return 0;
}

3 2 1
3 1 2
2 3 1
2 1 3
1 3 2
1 2 3