LeetCode 1198 — Find Smallest Common Element in All Rows

Given an m x n integer matrix mat where each row is sorted in non-decreasing order, find the smallest integer that appears in every row. Return the smallest such integer if it exists. Return -1 if no integer appears in all rows. I/O Contract Input: 2D integer array mat Output: a single integer Constraints 1 <= m, n <= 500 1 <= mat[i][j] <= 10^4 Each row of mat is sorted in non-decreasing order. Examples mat = [[1,2,3,4,5],[2,4,5,8,10],[3,5,7,9,11],[1,3,5,7,9]] => 5 mat = [[1,2,3],[4,5,6]] => -1 Interview note: you are expected to clarify edge cases and write your own test methods and test cases. Example Input [[1,2,3,4,5],[2,4,5,8,10],[3,5,7,9,11],[1,3,5,7,9]] Output 5