https://leetcode.com/problems/first-completely-painted-row-or-column/description/?envType=daily-question&envId=2025-01-20You are given a 0-indexed integer array arr, and an m x n integer matrix mat. arr and mat both contain all the integers in the range [1, m * n].Go through each index i in arr starting from index 0 and paint the cell in mat containing the integer arr[i].Return the smallest inde..