力扣 python 简单题 第二轮2

1221. 分割平衡字符串

class Solution:
    def balancedStringSplit(self, s: str) -> int:
        ans, d = 0, 0
        for ch in s:
            if ch == 'L':
                d += 1
            else:
                d -= 1
            if d == 0:
                ans += 1
        return ans

1252. 奇数值单元格的数目

class Solution:
    def oddCells(self, m: int, n: int, indices: List[List[int]]) -> int:
        rows = [0] * m
        cols = [0] * n
        for x, y in indices:
            rows[x] += 1
            cols[y] += 1
        oddx = sum(row % 2 for row in rows)
        oddy = sum(col % 2 for col in cols)
        # 奇加偶，偶加奇
        return oddx * (n - oddy) + (m - oddx) * oddy

1260. 二维网格迁移

一维展开

class Solution:
    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
        m, n = len(grid), len(grid[0])
        ans = [[0] * n for _ in range(m)]
        for i, row in enumerate(grid):
            for j, v in enumerate(row):
                index1 = (i * n + j + k) % (m * n)
                ans[index1 // n][index1 % n] = v
        return ans

1379. 找出克隆二叉树中的相同节点

class Solution:
    def getTargetCopy(self, original: TreeNode, cloned: TreeNode, target: TreeNode) -> TreeNode:
        if original is None or original is target:
            return cloned
        return self.getTargetCopy(original.left, cloned.left, target) or \
               self.getTargetCopy(original.right, cloned.right, target)