c++ - std::string::append(std::string) 错误输出

Question

我正在尝试制作一个简单的文本加密器(并非所有功能都是完整的)，但我有一个特定的问题需要一些帮助。我此时停止编码并添加了一些注释文档以进行测试:

在函数algorithm()中:第 16-25 行将 std::string ck[] 的索引 append 到 nested 循环内的 std::string KEY。 外部 循环正在运行以测量 PASSWORD.size() 并根据所有 ck[] 检查每个 PASSWORD.substr(...)。

然而，输出结果只是 PASSWORD 第一个和最后一个字符的索引值。例如。如果 PASSWORD=abc KEY 输出 0002。我希望整个 PASSWORD 成为 KEY(按照指示)。

#include <string.h>
#include <iostream>
#include <stdlib.h>
#include <sstream>


std::string PASSWORD, KEY, ENCRYPTED_TEXT;

void algorithm(std::string note){
    ENCRYPTED_TEXT.append(note);

    /**STANDARD RULESET**/
    std::string ck[] = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };

    for(int x=0;x<PASSWORD.size();x++){
        for(int y=0;y<sizeof(ck)/4;y++){ 
            if(PASSWORD.substr(x,x+1)==ck[y]){
                std::stringstream ind;
                if(y>9) ind << y+1;
                else ind << "0" << y;
                KEY.append(ind.str());
            }
        }
    }
    std::cout << "\nKey is " << KEY;

    //make_file(ENCRYPTED_TEXT);
}

void qn_setup(){
    bool ask=true;
    while(ask=true){
        std::string check1="", check2="";
        std::cout << "Type a password:\n";
        std::cin >> check1;
        std::cout << "Confirm password:\n";
        std::cin >> check2;
        if(check1==check2) { 
            PASSWORD=check1;
            ENCRYPTED_TEXT=check1;
            ask=false; 
            break; }
        else { std::cout << "\nPasswords did not match.\n"; }
    }
}

int main(){
    qn_setup();
    algorithm(""); //testing key
}

没有任何语法错误，只有逻辑错误。

Answer 1

string substr ( size_t pos = 0, size_t n = npos ) const;

Generate substring

Returns a string object with its contents initialized to a substring of the 
current object.

This substring is the character sequence that starts at character position 
pos and has a length of n characters.

所以你的支票必须是:

PASSWORD.substr(x,1)==ck[y] /* instead of PASSWORD.substr(x,x+1) */