算法1
(用algorithm库里的排序next_permutation())

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 7;
string a;
int main()
{
    char str[N];
    cin >> a;
    for (int i = 0; i < a.size(); i ++ ) str[i] = a[i];

    do{//先do的为了得到初试的结果
        for (int i = 0; i < a.size(); i ++ ) cout << str[i];
        cout << endl;
    } while (next_permutation(str, str + a.size()));
    return 0;
}

算法2
(DFS)
每次遍历所有可能，记录每次加入进去的状态

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 7;
string a;
bool st[N];
string res;
void dfs(string a, int cnt)
{
    if(cnt == a.size()){ cout << res << endl;return;}
    for(int i = 0; i < a.size(); i ++ )
    {
        if(!st[i]){//不在深搜栈内才能进入
            st[i] = true;//进入深搜栈
            res += a[i];//拼接字符串
            dfs(a,cnt + 1 );//递归
            st[i] = false;//回溯
            res.pop_back();
        }
    }
}
int main()
{
    cin >> a;
    dfs(a,0);
    return 0;
}

作者：NgAgo
链接：https://www.acwing.com/solution/content/55606/
来源：AcWing
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。