Find the next greater element for every element in an array?

Short answer: int[] NextGreaterElements(int[] nums) { int n = nums.Length; int[] result = new int[n]; Stack<int> stack = new Stack<int>(); for (int i = n - 1; i >= 0; i--) { while (stack.Count > 0 && stack.Peek() <= nums[i]) { stack.Pop(); } result[i] = stack.Count == 0 ? -1 : stack.Peek(); stack.Push(nums[i]); } return result; } Explanation: Traverse from right to left, use stack to keep track of next greater elements in O(n).

Example code

int[] NextGreaterElements(int[] nums) {
int n = nums.Length;
int[] result = new int[n];
Stack<int> stack = new Stack<int>();
for (int i = n - 1; i >= 0; i--) { while (stack.Count > 0 && stack.Peek() <= nums[i]) { stack.Pop(); }
result[i] = stack.Count == 0 ? -1 : stack.Peek(); stack.Push(nums[i]); }
return result;
} Explanation: Traverse from right to left, use stack to keep track of next greater elements in O(n).

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.