STL的排列函数及字符串的排序方法

next_permutation(a,a+n); 　　a代表数组的头地址，a+n代表数组的长度。

运用该函数，a数组将变成原排列的下一个排列。

与之相反的函数为prev_permutation(a,a+n);

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;

int f(int n) {
    int sum = 1;
    for(int i = 2; i <= n; i++)
        sum *= i;
    return sum;
}
int main() {
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int a[10];
    int n;
    scanf("%d",&n);
    for(int i = 1; i <= n; i++) {
        a[i] = i;
    }
    for(int i = 1; i <= f(n); i++)    {
        for(int j = 1; j <= n; j++)
            cout << a[j];
        next_permutation(a+1,a+n+1);    //prev_permutation(a+1,a+n+1);
        cout << endl;
    }
    return 0;
}

上面是int型，下面的char型和string型的写法

第一行为输入，后面几行为输出，上题的整型输出类似

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;

int f(int n) {
    int sum = 1;
    for(int i = 2; i <= n; i++)
        sum *= i;
    return sum;
}
int main() {
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    string b; //char a[100];
    cin >> b; //scanf("%s",a);
    sort(b.begin(), b.end()); //sort(a, a+stlen(a));
    for(int j = 1; j <= f(b.length()); j++) {// f(strlen(a))
        cout << b << endl; // printf("%s
",a);
    next_permutation(b.begin(),b.end()); // next_permutation(a, a+strlen(a));    
    }
    return 0;
}