排列和组合

递归生成排列和组合

void doPermute(char str[],char result[],bool used[],int length,int level){
    if(level==length){
        cout<<result<<endl;
        return;
    }

    for(int i=0;i<length;i++){
        if(!used[i]){
            result[level]=str[i];
            used[i]=true;
            doPermute(str,result,used,length,level+1);
            used[i]=false;
        }
    }
}

void permute(char* str){
    int len=strlen(str);
    char* result=new char[len+1];
    result[len]='\0';
    bool* used=new bool[len];
    memset(used,false,len*sizeof(bool));

    doPermute(str,result,used,len,0);

    delete []result;
    delete []used;
}

void doCombine(char str[],char result[],int length,int level,int start){
    for(int i=start;i<length;i++){
        result[level]=str[i];
        result[level+1]='\0';
        cout<<result<<endl;

        doCombine(str,result,length,level+1,i+1);
    }
}

void combine(char*str){
    int len=strlen(str);
    char* result=new char[len+1];

    doCombine(str,result,len,0,0);

    delete []result;
}