Python | Leetcode Python题解之第304题二维区域和检索-矩阵不可变

题目：

题解：

class NumMatrix:def __init__(self, matrix: List[List[int]]):m, n = len(matrix), (len(matrix[0]) if matrix else 0)self.sums = [[0] * (n + 1) for _ in range(m + 1)]_sums = self.sumsfor i in range(m):for j in range(n):_sums[i + 1][j + 1] = _sums[i][j + 1] + _sums[i + 1][j] - _sums[i][j] + matrix[i][j]def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:_sums = self.sumsreturn _sums[row2 + 1][col2 + 1] - _sums[row1][col2 + 1] - _sums[row2 + 1][col1] + _sums[row1][col1]