C語言-if語句問題

Question

我創建了以下程序來制作Caesar和Vigenere密碼。 我已經使Caesar密碼正常工作，但是我無法讓Vigenere正常工作。

我想發生的事情是讓我的if語句以5的間隔“捕獲”所有不同的數字。但是，每當我運行程序時，我的Viegenere密碼都會輸出完全相同的輸入。 我相信這是因為我在if語句中犯了一個錯誤，但是我不確定這是什么。

Viegenere密碼的開頭在代碼中被注釋為// Vigenere Cipher--關鍵字是“ apple”

#include <stdio.h>


int main(){
int i=0;
 //setting the individual slot number for the array-- later used in the while loop
char guy[100];
printf("Enter the plain text:");
fgets(guy,100,stdin); //takes user's input-- such as "abc" and puts it into its respective slot in the array guy[10] r-right?

while (guy[i] != '\0'){ //while loop that runs until it reaches the end of the string


    if ((guy[i]) >= 'A' && (guy[i]<= 'Z')){ //moves capital letter values up 1
        if (guy[i]=='Z'){
            guy[i]=guy[i]-25;
        }
        else {
        guy[i]=guy[i]+1; //makes the current "slot" number go up 1 value. Example: a = 97 + 1 -> b = 98
        }
        }
    if ((guy[i]) >= 'a' && (guy[i]) <= 'z'){// moves lower case letter values up 1
        if (guy[i]=='z'){
            guy[i]=guy[i]-25;
        }
        else{
        guy[i]=guy[i]+1;
        }
    }
    i++; //moves the array's interval up to the next "slot"

}
printf("Encrypted text is: %s\n",guy);

//Vigenere Cipher-- keyword is "apple"
//a = 1  value shift
//p = 16 value shift
//p = 16 value shift
//l = 17 value shift
//e = 5  value shift

printf("Enter the plain text: ");
fgets(guy,100,stdin);//takes user's input

while (guy[i] != '\0'){ //while loop that runs until it reaches the end of the string

    if (i%5==0 || i==0){ //checks to see which character it is in the string, for instance the numbers 0,5,10,15,20 should all be added by 1
    guy[i] = guy[i]+1;
    }

    if ((i-1)%5==0 || i==1){ //all numbers that are second in the key word 'apple', such as 1,6,11,16
        guy[i]=guy[i]+16;
    }
    if ((i-2)%5==0 || i==2){// all numbers that are third to the key word 'apple' , such as 2,7,12,17,22
        guy[i]=guy[i]+16;
    }
    if((i-3)%5==0 || i==3){// all numbers that are fourth to the key word 'apple', such as 3,8,13,18
        guy[i]=guy[i]+17;
    }
    if((i-4)%5==0 || i==4){// all numbers that are fifth in the key word 'apple', such as 4,9,14,19
        guy[i]=guy[i]+5;
    }
    else {
    i++;
    }
    }
printf("Encrypted text is: %s\n",guy);
}

Answer 1

在再次加密數據之前-您應該重新初始化變量“ i”的值

#include <stdio.h>


    int main(){
    int i = 0;
    //setting the individual slot number for the array-- later used in the  while loop
    char guy[100];
    printf("Enter the plain text:");
    fgets(guy, 100, stdin); //takes user's input-- such as "abc" and puts it into its respective slot in the array guy[10] r-right?

    while (guy[i] != '\0'){ //while loop that runs until it reaches the end of the string


        if ((guy[i]) >= 'A' && (guy[i] <= 'Z')){ //moves capital letter values up 1
            if (guy[i] == 'Z'){
                guy[i] = guy[i] - 25;
            }
            else {
                guy[i] = guy[i] + 1; //makes the current "slot" number go up 1 value. Example: a = 97 + 1 -> b = 98
            }
        }
        if ((guy[i]) >= 'a' && (guy[i]) <= 'z'){// moves lower case letter values up 1
            if (guy[i] == 'z'){
                guy[i] = guy[i] - 25;
            }
            else{
                guy[i] = guy[i] + 1;
            }
        }
        i++; //moves the array's interval up to the next "slot"

    }
    printf("Encrypted text is: %s\n", guy);

    //Vigenere Cipher-- keyword is "apple"
    //a = 1  value shift
    //p = 16 value shift
    //p = 16 value shift
    //l = 17 value shift
    //e = 5  value shift
    printf("The value of i = %d\n", &i);
    i = 0;
    printf("Enter the plain text: ");
    fgets(guy, 100, stdin);//takes user's input

    while (guy[i] != '\0'){ //while loop that runs until it reaches the end of the string

        if (i % 5 == 0 || i == 0){ //checks to see which character it is in the string, for instance the numbers 0,5,10,15,20 should all be added by 1
            guy[i] = guy[i] + 1;
        }

        if ((i - 1) % 5 == 0 || i == 1){ //all numbers that are second in the key word 'apple', such as 1,6,11,16
            guy[i] = guy[i] + 16;
        }
        if ((i - 2) % 5 == 0 || i == 2){// all numbers that are third to the key word 'apple' , such as 2,7,12,17,22
            guy[i] = guy[i] + 16;
        }
        if ((i - 3) % 5 == 0 || i == 3){// all numbers that are fourth to the key word 'apple', such as 3,8,13,18
            guy[i] = guy[i] + 17;
        }
        if ((i - 4) % 5 == 0 || i == 4){// all numbers that are fifth in the key word 'apple', such as 4,9,14,19
            guy[i] = guy[i] + 5;
        }
        else {
            i++;
        }
    }
    printf("Encrypted text is: %s\n", guy);
    getchar();
}

輸出： -

輸入純文本：apple加密文本為：bqqmf

i的值= 1900200-重新初始化之前的i的值。

輸入純文本：apple加密文本為：bÇÇ}