51Nod 1384 全排列

#include <iostream>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <map>
using namespace std;

char s[50];

bool cmp(char x,char y){
    return x < y;
}

int main(){
    cin >> s;
    int len = strlen(s);
    sort(s, s+len, cmp);
    //cout << s<< endl;
    do{
        cout<<s<< endl;
    }
    while(next_permutation(s,s+len));
    return 0;
}

回溯：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
char s[20];
int book[30],a[20],ans[20],n;

void dfs(int dis,int cnt)
{
    int i,j;
    if(cnt==n) {
        for(i=1;i<=n;i++) cout<<ans[i];
        cout<<endl;
        return;
    } 
    for(i=dis;i<n;i++) {
        if(book[i]==0) {
            book[i]=1;
            ans[cnt+1]=a[i];
            dfs(dis,cnt+1);
            book[i]=0;
            while(i<n && a[i]==a[i+1]) i++;
        }
    }
    
}


int main()
{
     ios::sync_with_stdio(false);  
    int i,j;
    cin>>s;
    n=strlen(s);
    for(i=0;i<n;i++) a[i]=s[i]-'0';
    sort(a,a+n);
    dfs(0,0);
    return 0;
}