Recursion

[whitedragon]

Hey people, I have a problem with recursion that I can't seem to solve. The code I've written so far is below:

18 int main(void) {
19 int temp, i, start, end, size =0, count =0, num[MAX_SIZE] = {0};
20
21 printf("Enter start and end: ");
22 scanf("%d %d", &start, &end);
23
24 while(start <= end) {
25 temp = start;
26 for(i=0;temp>0;i++) {
27 num[i] = temp % 10;
28 temp /= 10;
29 size++;
30 }
31 count += isPalindrome(num, size);
32 start++;
33 }
34
35 printf("Number of palindrome numbers = %d\n", count);
36
37 return 0;
38 }
39
40 // Return 1 if arr is a palindrome, or 0 otherwise.
41 // Driver function to call recursive function palindromeRecur()
42 int isPalindrome(int arr[], int size) {
43 int i=0;
44 return palindromeRecur(arr, i, size);
45 }
46
47 // Return 1 if arr is a palindrome, or 0 otherwise.
48 // Recursive function
49 int palindromeRecur(int arr[], int i, int size) {
50 if(size <= i)
51 return 1;
52
53 if(arr[i] != arr[size])
54 return 0;
55 else return palindromeRecur(arr, i+1, size-1);
56 }

[Athar]

Remove the line numbers and add code tags, the code is unreadable otherwise.

I have a problem

...such as?

[whitedragon]

int main(void) {
int temp, i, start, end, size =0, count =0, num[MAX_SIZE] = {0};

printf("Enter start and end: ");
scanf("%d %d", &start, &end);

// From start to end, numbers are passed into isPalindrome function to
// determine whether it is a palindrome. The 'count' of palindrome within
// this range is then printed.
while(start <= end) {
temp = start;
for(i=0;temp>0;i++) {
num[i] = temp % 10;
temp /= 10;
size++;
}
count += isPalindrome(num, size);
start++;
}

printf("Number of palindrome numbers = %d\n", count);

return 0;
}

// Return 1 if arr is a palindrome, or 0 otherwise.
// Driver function to call recursive function palindromeRecur()
int isPalindrome(int arr[], int size) {
int i=0;
return palindromeRecur(arr, i, size);
}

// Return 1 if arr is a palindrome, or 0 otherwise.
// Recursive function
int palindromeRecur(int arr[], int i, int size) {
if(size <= i)
return 1;

if(arr[i] != arr[size])
return 0;
else return palindromeRecur(arr, i+1, size-1);
}

My isPalindrome and palindromeRecur are unable to correctly determine a positive case. Every case is return 0. Thank you for your time.

[kameswarib]

Two problems with size values..

1. Line 53. Array size starts from 0 to (size-1). You are taking the ending index as size, instead of size-1. It should be:
if(arr[i] != arr[size-1])

2. size value should be reset to 0 before calculating for the next number.
Insert size=0; after line 25.
That should work.

Also, while posting code, please use the Source code format (in the formats section on the right) or use code tags.

Hope this helps.

[whitedragon]

Thank you, didn't realize I forgotten to re-initialize size after the first recursion is over.