Question

I want to sort an array .
SO i wrote this merge sort, it doesnt do what i want it to i.e sort, just stalls !
im going over the algorithm again and again, and i feel this is so correct, but no !
please take a look and tell me what might be wrong.

void mergeSort(int *arr, int low, int high){
int mid = (low+high)/2;
while(low<high){
    mergeSort(arr, low, mid);
    mergeSort(arr, mid+1, high);
    merge(arr, low, high, mid);
}
}

void merge(int *arr,int low, int high, int mid){
int i =low,j=mid+1,k=0;
int temp[50];  // should i new/malloc this with size of ( high -low +1) ?
while(i<=mid && j<=high){
    if(arr[i]<arr[j])
        temp[k++] = arr[i++];
    else
        temp[k++] = arr[j++];
}
while(i<=mid)
    temp[k++] = arr[i++];
while(j<=high)
    temp[k++] = arr[j++];
for(int x = 0; x<=high; x++){
    arr[x]=temp[x];
}
}

Answer 1

void mergeSort(int *arr, int low, int high){
    int mid = (low+high)/2;
    while(low<high){

if the loop is entered at all, it is an infinite loop since neither low nor high are changed.

        mergeSort(arr, low, mid);
        mergeSort(arr, mid+1, high);
        merge(arr, low, high, mid);
    }
}

void merge(int *arr,int low, int high, int mid){
    int i =low,j=mid+1,k=0;
    int temp[50];  // should i new/malloc this with size of ( high -low +1) ?

Yes, you should definitely allocate the correct amount of storage.

    while(i<=mid && j<=high){
        if(arr[i]<arr[j])

That should better be arr[i] <= arr[j] to have a stable sort, though that doesn’t matter for ints.

            temp[k++] = arr[i++];
        else
            temp[k++] = arr[j++];
    }
    while(i<=mid)
        temp[k++] = arr[i++];
    while(j<=high)
        temp[k++] = arr[j++];
    for(int x = 0; x<=high; x++){

That should be for(int x = low; ....

        arr[x]=temp[x];

arr[x] = temp[x-low]; (or use two indices).

    }
}