why I am not getting any output even no errors so that I could figure out what changes should I made.

should I change the compiler?

Please help me in simple words thanks a lot.

#include <stdio.h>
#include <string.h>

char* words[] = {"rar", "tokyo", "level", "prefix", "mom", "delhi", "naruto"};
int size = sizeof(words) / sizeof(words[0]);

void palindChecker(char **, int);

int main() {
    palindChecker(words, size);

    return 0;
}

void palindChecker(char **array, int len) {
    int tempStrLen, tempStrLen1;
    for (int i = 0; i < len; i  ) {
        tempStrLen = strlen(array[i]);
        if (tempStrLen1 <= tempStrLen) {
            tempStrLen1 = tempStrLen;
        }
    }
    char tempStr[tempStrLen1];
    for (int i = 0; i < len; i  ) {
        strcpy(tempStr, strrev(array[i]));
        if (strcmp(strrev(tempStr), array[i]) == 0) {
            printf("%s is palindrome\n", array[i]);
        }
        else {
            printf("%s is not palindrome\n", array[i]);
        }
    }
}

CodePudding user response：

Your code as multiple problems:

• tempStrLen1 is not initialized when calculating the maximum string length
• Once the maximum string length is calculated, the allocated array is too short (remember: a string additionally needs a terminating 0)
• strrev() reverses a string in place, i.e. it modifies the passed string. This will not work for array[i] as these strings are constants and are protected from modification.
• Even if it worked, the code assumes that the original string is not modified.

The below code fixes the problems.

void palindChecker(char **array, int array_len) {
    // calculate maximum string length
    int str_len = 0;
    for (int i = 0; i < array_len; i  ) {
        int len = strlen(array[i]);
        if (str_len < len)
            str_len = len;
    }

    char tempStr[str_len   1];

    for (int i = 0; i < array_len; i  ) {

        // create modifiable copy
        strcpy(tempStr, array[i]);
        // reverse copy
        strrev(tempStr);

        if (strcmp(tempStr, array[i]) == 0) {
            printf("%s is palindrome\n", array[i]);
        }
        else {
            printf("%s is not palindrome\n", array[i]);
        }
    }
}

CodePudding user response：

You need to initialize initially the variable tempStrLen1 before the for loop

int tempStrLen, tempStrLen1;
for (int i = 0; i < len; i  ) {
    tempStrLen = strlen(array[i]);
    if (tempStrLen1 <= tempStrLen) {
        tempStrLen1 = tempStrLen;
    }
}

like

int tempStrLen, tempStrLen1 = 0;

Otherwise the function invokes undefined behavior.

Also you need to define the variable length array tempStr with one more element like

char tempStr[tempStrLen1   1];

A more serious bug of the function that you are trying to apply the non-standard function strrev to a string literal that again invokes undefined behavior

strcpy(tempStr, strrev(array[i]));

You need to write instead

strcpy(tempStr, array[i]);
strrev( tempStr );

Pay attention to that to determine whether a string represents a palindrome there is no need to create its copy. Instead you could just write

for ( int i = 0; i < len; i   )
{
    size_ j = 0;
    size_t n = strlen( array[i] );

    while ( j < n / 2 && array[i][j] == array[i][n - j - 1] )    j;
        
    if (  j == n / 2 ) {
        printf("%s is palindrome\n", array[i]);
    }
    else {
        printf("%s is not palindrome\n", array[i]);
    }
}

CodePudding user response：

One addition to @Codo's answer. You don't need two for loops in your function.

void palindChecker(char **array, int len)
{
    for (int i = 0; i < len; i  )
    {
        int tempStrLen = strlen(array[i]);

        char tempStr[tempStrLen 1];
        
        strcpy(tempStr, array[i]);
        strrev(tempStr);
        if (strcmp(tempStr, array[i]) == 0)
        {
            printf("%s is palindrome\n", array[i]);
        }
        else
        {
            printf("%s is not palindrome\n", array[i]);
        }
    }
}