UberOA #52
Minimum Obstacle Removal
估计中等评测数据准备中，可先阅读题面
考点（AI 标注）网格搜索模拟/实现
You are given a 2d matrix which consist of the following symbols ".", "#", "|", where "." represent free cell, "#" represent a obstacle, "|" denotes shape. Your task is to find out the minimum obstacle to remove from the matrix so that the shapes falls down to the bottom.
Constraints
N/A
Example 1
Input:
matrix = [["*", "*", "*", "*"], ["#", "*", ".", "*"], [".", ".", "#", "."], [".", "#", ".", "#"]]
Output:
4
Explanation: Hence, return 4.