凯撒密码实现

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#include <stdio.h>   int main() {     // 凯撒加密，明文中字母按字母表左移或者右移三位,这里右移     char input[6] = "hello";     char output[6];     int key = 3;     int i,j;     for (i = 0; i < 5; i++)     {         int a = input[i];         a += 3;         output[i] = (char)a;     }     output[i] = '\0';     printf("加密后：%s\n", output);       for (j = 0; j < 5; j++)     {         int b = output[j];         b -= 3;         input[j] = (char)b;     }     input[j] = '\0';     printf("解密后：%s", input);     return 0; }