c++ - what(): basic_string::_M_construct null 无效错误

Question

#include<iostream>
#include<string>
using namespace std;
string generateKey(string str, string key)
{
    int x = str.size();
    for(int i=0; ;i++)
    {
        if(x==i)
            i=0;
        if(key.size() == str.size())
            break;
        key.push_back(key[i]);
    }
    return key;
}
string cipherText(string str, string key)
{
    string cipher_text;
    for(int i=0; i<str.size(); i++)
    {
        int x=(str[i]+key[i])%26;
        x+='A';
        cipher_text.push_back(x);
    }
    return cipher_text;
}
string originalText(string cipher_text, string key)
{
    string orig_text;
    for(int i=0;i<cipher_text.size(); i++)
    {
        int x=(cipher_text[i]-key[i] +26)%26;
        x +='A';
        orig_text.push_back(x);
    }
    return orig_text;
}
int main()
{
    int x;
    cout<<"Enter your choice"<<endl;
    cout<<"1. Mono-alphabetic\n2. Poly-alphabetic\n";
    cin>>x;
    switch(x)
    {
    case 1:
        cout<<"Mono-alphabetic cipher"<<endl;
        cout<<"Enter your choice \n 1.Encryption\n 2.Decryption\n";
        int b;
        cin>>b;
        switch(b)
        {
        case 1:
            int k,i;
            char plainText[100];
            cout<<"Encryption\n";
            cout<<"Enter Plain text"<<endl;
            cin>>plainText;
            cout<<"Enter Encryption key"<<endl;
            cin>>k;
            for(i=0;(i<100 && plainText[i]!='\0');i++)
            plainText[i]=plainText[i]+k;
            cout<<"\n Encrypted text:"<<plainText<<endl;
            break;
        case 2:
            int d;
            char encrypedText[100];
            cout<<"Decryption\n";
            cout<<"Enter Encrypted text"<<endl;
            cin>>encrypedText;
            cout<<"Enter Decryption key"<<endl;
            cin>>d;
            for(i=0;(i<100 && encrypedText[i]!='\0');i++)
            encrypedText[i]=encrypedText[i]-d;
            cout<<"\n Decrypted text:"<<encrypedText<<endl;
            break;
        default:
            cout<<"WRONG Choice Entered!!!\n";
            break;
        }
    case 2:
        {
    cout<<"Poly-alphabetic"<<endl;
    string str ="PLANTTHATBOMBTHERE";
    string keyword="AMAZON";
    string key =generateKey(str,key);
    string cipher_text = cipherText(str,key);
    cout<<"Ciphertext:"<<cipher_text<<endl;
    cout<<"Original text:"<<originalText(cipher_text, key);
    break;
        break;
        }
    }

}

此代码用于替换密码，多字母密码部分未运行，显示 std::logic_error 错误和 what(): basic_string::_M_construct null not valid 错误请帮助第一部分运行正常，没有任何错误，但多字母密码部分不显示任何编译错误它只显示运行时错误

标签： c++stringlogicstd

Answer 1

string keyword="AMAZON";
string key =generateKey(str,keyword);
string cipher_text = cipherText(str,key);
cout<<"Ciphertext:"<<cipher_text<<endl;

您正在使用 key 变量作为参数在它获取内存之前运行。试试上面的代码。