内存分配，输出垃圾

Question

为什么这会在 arrayLetter 中输出垃圾而不是 char 值？ 当我将for循环打印在方法调用上方的arrayLetter时，它起作用了；当我把它放在它下面时，它不起作用。我没有在方法或主体中更改 arrayLetter。这是一个简单的程序，可以移动索引并输出移动的字母。

#include <stdio.h>
#include <stdlib.h>

int* getMatchedIndex(char arrayLetter[], char plainTextExample[],int sizeArrayLetter, int sizePlainTextExample);
int* vigenereCipherEncryptIndex(int key[], int sizeKey, int sizeArrayLetter, int sizePlainTextExample, int arrayMatchAtIndex[]);
char* convertToNewEncryptedArray(char arrayLetter[], int encryptArray[], int sizeArrayLetter, int sizePlainTextExample);

int main(void) {

    char arrayLetter[] = { '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'};

    int key[] = { 21, 4, 2, 19, 14, 17};

    char plainTextExample[] = { 'h', 'e', 'r', 'e',
                                'i', 's',
                                'h', 'o', 'w',
                                'i', 't',
                                'w', 'o', 'r', 'k', 's'};

    int sizeArrayLetter = sizeof(arrayLetter)/sizeof(arrayLetter[0]);
    int sizePlainTextExample = sizeof(plainTextExample)/sizeof(plainTextExample[0]);
    int sizeKey = sizeof(key)/sizeof(key[0]);

    int *arrayMatchAtIndex;
    int *encryptArray;
    char *cipherArray;

    arrayMatchAtIndex = getMatchedIndex(arrayLetter, plainTextExample, sizeArrayLetter, sizePlainTextExample);
    encryptArray = vigenereCipherEncryptIndex(key, sizeKey, sizeArrayLetter, sizePlainTextExample, arrayMatchAtIndex);
    cipherArray = convertToNewEncryptedArray(arrayLetter, encryptArray, sizeArrayLetter, sizePlainTextExample);

    for(char i=0; i < sizeArrayLetter; i++)
    {
        //printf("%s%i%s", "Indexes of Encryption: ", encryptArray[i], " \n");
        printf("%s", arrayLetter);

    }


    free(arrayMatchAtIndex);
    free(encryptArray);
    free(cipherArray);

    return EXIT_SUCCESS;
}

//compare arrays and store index into array
int *getMatchedIndex(char arrayLetter[], char plainTextExample[],int sizeArrayLetter, int sizePlainTextExample)
{

    int* arrayMatchAtIndex = malloc(sizePlainTextExample* sizeof(int));

    //loop plainTextExample
    for(int i=0; i < sizePlainTextExample ; i++)
    {
        //loop arrayLetter
        for(int j=0; j < sizeArrayLetter ; j++)
        {
            //compare -> match then store arrayLetter index into arrayMatchAtIndex
            if(plainTextExample[i] == arrayLetter[j])
            {
                arrayMatchAtIndex[i] = j;
            }
        }

    }
    return arrayMatchAtIndex;
}

//encrypt array by adding 'key' indexes into array
int* vigenereCipherEncryptIndex(int key[], int sizeKey, int sizeArrayLetter, int sizePlainTextExample, int arrayMatchAtIndex[])
{
    //make new array
    int* encryptArray = malloc(sizePlainTextExample* sizeof(int));

    int j=0;

    //encrypt element -> (add elements of arrayIndexes and key) mod 26
    for(int i=0; i < sizePlainTextExample; i++)
    {

        if(i >= sizeKey)
        {
            j = (i % sizeKey);
            key[i] = key[j];
        }

        encryptArray[i] = (arrayMatchAtIndex[i]+key[i]) % 26;
    //  printf("%s%d%s%d%s", "Match Element: ", arrayMatchAtIndex[i], " key ", key[i], " ");
    //  printf("%s%d%s", "encryptElement: ", encryptArray[i], " \n");
    }

    return encryptArray;
}

//convert encrypt array index to its elements
char* convertToNewEncryptedArray(char arrayLetter[], int encryptArray[], int sizeArrayLetter, int sizePlainTextExample)
{
    char* cipherArray = malloc(sizePlainTextExample* sizeof(int));

    //encrypted index - > convert elements to new index
    for(int i=0; i < sizePlainTextExample ; i++)
    {
        for(int j=0; j< sizeArrayLetter; j++)
        {
            //find index->match then put Encrypted index into letter element
            if(encryptArray[i] == j)
            {
                cipherArray[i] = arrayLetter[j];
                printf("%c", arrayLetter[2]);
            }

        }
    }

    return cipherArray;
}

Answer 1

正如 Jonathan Leffler 所说，您的数组只是一个数组，而不是 C 字符串（以 nul 结尾的字符序列）。 %s 仅与 C 字符串一起使用。

将循环更改为：

for (char i=0; i<sizeArrayLetter; i++) {
    putchar(arrayletter[i]);
}
putchar('\n');

这将单独打印数组中的所有字符和一个额外的行尾。