Count Same-Color Squares in Matrix

LeetCode 221 variant — count maximal same-color square sub-grids. DP on each cell as the bottom-right corner. Requirements Input: m × n grid of colored cells. Output: count of square sub-grids whose cells are all the same color (or maximum side length, depending on prompt). DP: dp[i][j] = 1 + min(dp[i-1][j], dp[i][j-1], dp[i-1][j-1]) if grid[i][j] == grid[i-1][j] == grid[i][j-1] == grid[i-1][j-1] else 1. Sum dp[i][j] across the grid for the count variant; max for the side variant. Examples The plain "count all-1 squares" DP generalizes to same-color directly. Notes Variant reported in both intern VO and an additional NG round. Common bug: assuming all four corners equal is sufficient — need all three neighbors (top, left, top-left) to match the current cell. Preparation Write the all-1-squares DP from memory in under 8 min. Generalize to multi-color in <2 min — only the equality check changes.