Why is this merge sort implementation not working?

Question

I am missing something embarrassingly basic here in my Merge Sort implementation:

# include <math.h>
# include <stdio.h>

int temp[10];

void merge_sort(int *indices, int x, int z);
void m_merge(int *indices, int x, int y, int z);


void merge_sort(int *indices, int x, int z )
{
        int y;
        if(x<z){
                y = (x+z)/2;
                merge_sort(indices,x,y);
                merge_sort(indices,y+1,z);
                my_merge(indices,x,y,z);
        }
}

void my_merge(int *indices, int x, int y, int z)
{
        int mark1=x, mark2=y+1;
        int cnt=0;

        while(mark1 <= y && mark2 <= z){
                if (indices[mark1] < indices[mark2])
                        temp[cnt++] = indices[mark1++];
                else
                        temp[cnt++] = indices[mark2++];
        }
        while(mark1 <= y)
                temp[cnt++] = indices[mark1++];

        while(mark2 <= z)
                temp[cnt++] = indices[mark2++];

}

int main(int argc, char **argv)
{
        int arr[] = {1,5,8,7,4,30,-87,100,200,300};
        int i; 
        merge_sort(arr,0,9);

        for(i=0;i<=9;i++)
                printf(" %d \n  ",temp[i]);

        return 0;
}

Why is not working, as it should? I have checked and re-checked again, but I do not get the sorted array. What am I missing here?

This is what I get: 1 5 8 7 4 30 -87 100 200 300

You may vote it down, but I am myself very embarassed to ask this here.

Answer 1

my_merge() merges the numbers into temp[], but never copies them back into indices[]. Copy them back into the correct location and it should work.