Mergesort?

Short answer: void MergeSort(int[] arr, int left, int right) {

Example code

if (left < right)
{
int mid = (left + right) / 2; MergeSort(arr, left, mid); MergeSort(arr, mid + 1, right); Follow on: Merge(arr, left, mid, right); }
} void Merge(int[] arr, int left, int mid, int right) {
int n1 = mid - left + 1;
int n2 = right - mid;
int[] L = new int[n1];
int[] R = new int[n2]; Array.Copy(arr, left, L, 0, n1); Array.Copy(arr, mid + 1, R, 0, n2); int i = 0, j = 0, k = left; while (i < n1 && j < n2) arr[k++] = (L[i] <= R[j]) ? L[i++] : R[j++];
while (i < n1) arr[k++] = L[i++];
while (j < n2) arr[k++] = R[j++];
} Explanation: Divide array, sort left & right halves, then merge sorted halves.

Real-world example (ShopNest)

In coding rounds, state complexity aloud, write a clear ShopNest-flavored example (orders, carts), then handle edge cases (empty list, null, overflow).

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.