LeetCode 947. Most Stones Removed with Same Row or Column 解题报告（python）

947. Most Stones Removed with Same Row or Column

947. Most Stones Removed with Same Row or Column python solution

题目描述

On a 2D plane, we place stones at some integer coordinate points. Each coordinate point may have at most one stone.

Now, a move consists of removing a stone that shares a column or row with another stone on the grid.

What is the largest possible number of moves we can make?

解析

本题想要我们移动尽可能多的石子

横或者纵坐标相等的石子会互相链接构成一个区域。

可移动石子最多数目就是，石子的总数减去独立区域的个数

class Solution:
    def removeStones(self, stones: List[List[int]]) -> int:
        UF = {}
        def find(x):
            if x != UF[x]:
                UF[x] = find(UF[x])
            return UF[x]
            
        def union(x, y):
            UF.setdefault(x, x)
            UF.setdefault(y, y)
            UF[find(x)] = find(y)

        for i, j in stones:
            union(i, ~j)
        return len(stones) - len({find(x) for x in UF})

Reference

https://leetcode.com/problems/most-stones-removed-with-same-row-or-column/discuss/197668/Count-the-Number-of-Islands-O(N)