字符串的C递归置换算法 – >不跳过重复

我很难找到一个简单的语句来跳过这个递归排列代码的重复项.我到处看,似乎只找到使用swap或 java的例子.从我收集的内容来看,我认为我需要在for-loop之后放一条线.

谢谢！

#include "genlib.h"
#include "simpio.h"
#include <String>
#include <iostream>

void ListPermutations(String prefix,String rest);


int main() {

    cout << "Enter some letters to list permutations: ";
    String str = GetLine();
    cout << endl << "The permutations are: " << endl;
    ListPermutations("",str);

    return 0;
}

void ListPermutations(String prefix,String rest)
{
    if (rest == "") 
    {
        cout << prefix << endl;
    } 
    else 
    {   
        for (int i = 0; i < rest.length(); i++) 
        {
            if (prefix != "" && !prefix[i]) conTinue; // <--- I tried adding this,but it doesn't work
            cout << endl<< "prefix: " << prefix << " | rest: " << rest << endl;     
            String newPrefix = prefix + rest[i];
            String newRest = rest.substr(0,i) + rest.substr(i+1);  
            ListPermutations(newPrefix,newRest);           
        }    
    }
}

void ListPermutations(String prefix,String rest)
{
if (rest == "") 
{
    cout << prefix << endl;
} 
else 
{   
    for (int i = 0; i < rest.length(); i++) 
    {


        //test if rest[i] is unique.
        bool found = false;
        for (int j = 0; j < i; j++) 
        {
            if (rest[j] == rest[i])
                found = true;
        }
        if(found)
            conTinue;
        String newPrefix = prefix + rest[i];
        String newRest = rest.substr(0,i) + rest.substr(i+1);  
        ListPermutations(newPrefix,newRest);           
    }    
}
}