arrays - Writing Merge Sort Pseudo-Code Procedure in C

Question

I have been going through Introduction to Algorithms, and have been trying to implement the MERGE-SORT algorithm in C programming language to gain a better understanding of it.

The book presents two pseudo-codes:

and

While I do understand the above procedures, I must be missing something during the implementation.

I must be missing something from the pseudo-code but cannot figure it out yet. Any suggestions as to why this is happening would be appreciated.

EDIT: Updated Code and Output

/* C program for Merge Sort */
#include<stdlib.h>
#include<stdio.h>

void MERGE(int [], int , int , int );
void printArray(int [], int );
void MERGE_SORT(int [], int , int );

int main(void)
{
   int A[] = { 12, 11, 13, 5, 6, 7, 2, 9 };
   int arr_size = sizeof(A) / sizeof(A[0]);

   printf("Given array is 
");
   printArray(A, arr_size);

   MERGE_SORT(A, 0, arr_size); //Fixed: Index to start from zero

   printf("
Sorted array is 
");
   printArray(A, arr_size);

   return 0;
}

void MERGE(int A[], int p, int q, int r)
{
   int i = 0;
   int j = 0;
   int n1 = q - p + 1;                  //Computing length of sub-array 1
   int n2 = r - q;                      //Computing length of sub-array 2
   int *L = malloc((n1 + 2) * sizeof(*L + 1));        //Creating Left array
   int *R = malloc((n2 + 2) * sizeof(*R + 1));        //Creating Right array

   for (int i = 0; i <= n1; i++) { //Fixed: <=, i start from 0
       L[i] = A[p + i - 1];
   }
   for (int j = 0; j <= n2; j++) { //Fixed: <=, i start from 0
       R[j] = A[q + j];
   }

   L[n1 + 1] = 99;  //Placing Sentinel at the end of array
   R[n2 + 1] = 99;

   i = 1;
   j = 1;

   /*Prior to the first iteration k = p, so the subarray is empty.
   Both L[i] and R[j] are the smallest elements of their arrays and have not
   been copied back to A*/
   for (int k = p; k <= r; k++) { //Fixed: <=
       if (L[i] <= R[j]) {
           A[k] = L[i];
           i++;
       }
       else { //Fixed: Assignment and not condition check for A[k]
           A[k] = R[j];
           j++;
       }
   }

   free(L);
   free(R);
}

void MERGE_SORT(int A[], int p, int r)
{
   //During first iteration p = 1 & r = 8
   if (p < r) {
       int q = (p + r) / 2;
       MERGE_SORT(A, p, q);
       MERGE_SORT(A, q + 1, r);
       MERGE(A, p, q, r);
   }
}

/* Function to print an array */
void printArray(int Arr[], int size)
{
   int i;
   for (i = 0; i < size; i++)
       printf("%d ", Arr[i]);
   printf("
");
}

Answer 1

Looked in the pseudo code and found out that some things have been mistakenly written wrong.
1. You need to be careful with the array index to start from 0 or 1
2. Merge last part in for loop is actually an assignment instead for conditional check.

Edit: Have updated the code to fix for the error Stack around the variable A was corrupted

Please find the corrected code here(Lookout for //Fixed for fixes)

/* C program for Merge Sort */
#include<stdlib.h>
#include<stdio.h>

void MERGE(A, p, q, r);
void printArray(Arr, size);
void MERGE_SORT(A, p, r);

int main(void)
{
   int A[] = { 12, 11, 13, 5, 6, 7, 2, 9 };
   int arr_size = sizeof(A) / sizeof(A[0]);

   printf("Given array is 
");
   printArray(A, arr_size);

   MERGE_SORT(A, 0, arr_size - 1); //Fixed: Index to start from zero, arr_size - 1

   printf("
Sorted array is 
");
   printArray(A, arr_size);

   return 0;
}

void MERGE(int A[], int p, int q, int r)
{
   int i = 0;
   int j = 0;
   int n1 = q - p + 1;                  //Computing length of sub-array 1
   int n2 = r - q;                      //Computing length of sub-array 2
   int *L = malloc((n1+1) * sizeof(*L+1));          //Creating Left array
   int *R = malloc((n2+1) * sizeof(*R+1));          //Creating Right array
   for (int i = 0; i < n1; i++) { //Fixed: i start from 0
       L[i] = A[p + i];

   }
   // int arr_size = sizeof(A) / sizeof(A[0]);
   for (int j = 0; j < n2; j++) { //Fixed: j start from 0
       R[j] = A[q + j + 1];

   }

   L[n1] = 99;  //Placing Sentinel at the end of array
   R[n2] = 99;

   i = 0; //Fixed: i and j to start from 0
   j = 0;

   /*Prior to the first iteration k = p, so the subarray is empty.
   Both L[i] and R[j] are the smallest elements of their arrays and have not
   been copied back to A*/
   for (int k = p; k <= r; k++) { //Fixed: <=
       if (L[i] <= R[j]) {
           A[k] = L[i];
           i++;
       }
       else { //Fixed: Assignment and not condition check for A[k]
        A[k] = R[j];
        j++;
       }
   }

   free(L);
   free(R);
}

void MERGE_SORT(int A[], int p, int r)
{
   //During first iteration p = 1 & r = 8
   if (p < r) {
       int q = (p + r) / 2;
       MERGE_SORT(A, p, q);
       MERGE_SORT(A, q + 1, r);
       MERGE(A, p, q, r);
   }
}

/* Function to print an array */
void printArray(int Arr[], int size)
{
   int i;
   for (i = 0; i < size; i++)
       printf("%d ", Arr[i]);
   printf("
", size);
}

Hope it helps.
Revert for any doubts.