Leetcode 2282. Number of People That Can Be Seen in a Grid

Given an m×n grid of heights representing people, determine for each person how many other people they can see along the four cardinal directions where visibility stops at the first person of equal or greater height; return the per-person counts or the total number meeting some visibility criterion. The core challenge is efficient row/column scanning (often using monotonic stacks) to avoid costly brute-force checks.