将“the result of 3 and 2 is not 8”进行加密。加密时每个字符依次反复加上“4962873”中的数字，如果范围超过ASCII码的032（空格）~122（'z'）。则进行模运算
#include<iostream>
using namespace std;
char *qaz(char *a)
{
     int b[7]={4,9,6,2,8,7,3};
     for(int i=0;i<strlen(a);i++)
     {
             a[i]=a[i]+b[i%7];
             if(a[i]>'z')
             a[i]=031+a[i]%122;
     }
     return a;
}            
int main()
{
    char a[]="the result of 3 and 2 is not 8";
    cout<<"原字符串为:"<<a<<endl;
    cout<<"加密后:"<<qaz(a)<<endl;
    system("pause");
    return 0;
}
我的算法错哪里了，希望高手指点

你可以试着把加密后的字符串解密看能否还原回去.顺便贴上我的加密程序可能有些臃肿,算法也简单.

// 简单的字符加密程序.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <iomanip>
#include <cstring>

using std::cin;
using std::cout;
using std::endl;
using std::setw;


int _tmain(int argc, _TCHAR* argv[])
{
    const int MAX = 30;
    char key;
    int count = 0;
    char Str1[MAX];
    char Str2[MAX];

    for(int flag = 1;flag != 0;)
    {
        cout << "请输入密码:";
        cin >> Str1;
        cout << "加密请输入Y/y,解密请输入N/n :";
        cin >> key;
   
        if( key == 'y' || key == 'Y')
        {
            for(int T = 0;T <= strlen(Str1) - 1;T++)
            {       
                if( T % 2 == 0 )
                    Str2[T] = Str1[T + 1];
                else
                    Str2[T] = Str1[T - 1];
            }
        for( int i = strlen(Str1) - 1;i != -1;i--)
        {
            Str1[count] = Str2[i];
            count += 1;
        }
        for(int i = 0;i <= strlen(Str1) - 1; i++)
        {
            if( Str1[i] == 'A' || Str1[i] == 'a')
                Str1[i] = Str1[i] + 3;
            else
                if( Str1[i] == 'Z' || Str1[i] == 'z')
                Str1[i] = Str1[i] - 3;
            else
                Str1[i] = Str1[i] + 1;
        }
        for(int T = 0;T <= strlen(Str1) - 1;T++)
            cout << Str1[T];
        }
        else
            if( key == 'n' || key == 'N')
        {
            for(int i = 0;i <= strlen(Str1) - 1; i++)
        {
            if( Str1[i] == 'D' || Str1[i] == 'd')
                Str1[i] = Str1[i] - 3;
            else
                if( Str1[i] == 'W' || Str1[i] == 'w')
                Str1[i] = Str1[i] + 3;
            else
                Str1[i] = Str1[i] - 1;
        }
            for( int i = strlen(Str1) - 1;i != -1;i--)
        {
            Str2[count] = Str1[i];
            count += 1;
        }
            for(int T = 0;T <= strlen(Str1) - 1;T++)
            {
                if( T % 2 == 0 )
                    Str1[T] = Str2[T + 1];
                else
                    Str1[T] = Str2[T - 1];
            }
            for(int T = 0;T <= strlen(Str1) - 1;T++)
            cout << Str1[T];
            }
            cout << endl
                << "继续请输入一个非0的值..." << endl;
            cin >> flag;
            cout << endl;
            count = 0;
}
    cout << endl
         << "Press any key...";

    _getch();
    return 0;
}