题目：原题链接（中等）
标签：数组、动态规划
解法 | 时间复杂度 | 空间复杂度 | 执行用时 |
Ans 1 (Python) | 构造 = O ( N × M ) ; 查询 = O ( 1 ) | O ( N × M ) | 68ms (94.43%) |
Ans 2 (Python) | |||
Ans 3 (Python) |
解法一：
class NumMatrix:
def __init__(self, matrix: List[List[int]]):
if not matrix or not matrix[0]:
self.dp = None
else:
m, n = len(matrix), len(matrix[0])
self.dp = [[0] * (n + 1) for _ in range(m + 1)]
for i in range(1, m + 1):
for j in range(1, n + 1):
self.dp[i][j] = matrix[i - 1][j - 1] + self.dp[i][j - 1] + self.dp[i - 1][j] - self.dp[i - 1][j - 1]
def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
if self.dp is not None:
return self.dp[row2 + 1][col2 + 1] - self.dp[row2 + 1][col1] - self.dp[row1][col2 + 1] + self.dp[row1][col1]
else:
return 0
