ME 6 ko na di gumagana

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

void swap(int *a, int *b)
{
   int t;
   t  = *b;
   *b = *a;
   *a = t;
}

void insertion_sort(int A[], int from, int to) {
    for(int i = from; i < to; i++) {
        for(int j = i + 1; j > from && A[j] < A[j - 1]; j--) {
            int temp = A[j - 1];
            A[j - 1] = A[j];
            A[j] = temp;
        }
    }
}

int find_median(int A[],int p,int r)
{
    int n = r-p+1;
    insertion_sort(A,p,r);
    return A[n+1/2];
}

int quick_select(int A[], int p, int r, int k);

int median_of_medians(int A[],int p, int r)
{
    int N = r-p+1;
    int copy[N+1];
    for (int i = 1; i<=N; i++)
    {
        copy[i] = A[i];
    }

    int groups_no = ceil(N/5);
    int medians[groups_no+1];
    for(int i = 0;i < groups_no;i++)
    {
        if(i == groups_no-1) //last group
        {
            insertion_sort(copy,(i*5)+1,N);
            int group_length = N - ((i*5)+1) + 1;
            int median_ind = (group_length+1)/2 - 1;
            medians[i] = copy[(i*5)+1+median_ind];
        }
        else
        {
            insertion_sort(copy,(i*5)+1,(i*5)+5);
            int group_length = ((i*5)+5) - ((i*5)+1) + 1;
            int median_ind = (group_length+1)/2 - 1;
            medians[i] = copy[(i*5)+1+median_ind];

        }

    }

    if(groups_no > 5)
    {
        return quick_select(medians,1,groups_no,(groups_no+1)/2);
    }
    else
    {
        return medians[(groups_no+1)/2];
    }


}

int partition(int A[], int p, int r){
    int M = (r-p)+1;
    int median = median_of_medians(A,p,r);
    int ind;
    for(int i = p;i<=r;i++)
    {
        if(A[i]== median)
        {
            ind = i;
        }
    }
    swap(&A[ind],&A[r]);
    int x = A[r];
    int i = p-1;
    for(int j = p;j<=(r-1);j++)
    {
        if(A[j] <= x)
        {
            i++;
            swap(&A[i],&A[j]);
        }
    }
    swap(&A[i+1],&A[r]);
    return i+1;
}

int quick_select(int A[], int p, int r, int rank){
    if(p == r)
    {
        return A[p];
    }
    int q = partition(A,p,r);
    int k = q-p+1;
    if(rank == k)
    {
        return A[q];
    }
    else if (rank < k)
    {
        return quick_select(A,p,q-1,rank);
    }
    else
    {
        return quick_select(A,q+1,r,rank-k);
    }
}

int main(){
    int T, M;
    scanf("%d", &T);
    while(T-- > 0){
        scanf("%d", &M);
        int arr[M+1];

        //read the elements of the input array
        for(int i=1; i<=M; i++){
            scanf("%d",&arr[i]);
        }

        int median_index = ((M+1)/2);
        printf("Median: %d\n", quick_select(arr, 1, M, median_index));
    }
}