-
Notifications
You must be signed in to change notification settings - Fork 4
/
range_sum_query_2d_immutable.py
71 lines (53 loc) · 2.31 KB
/
range_sum_query_2d_immutable.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
"""
304. 二维区域和检索 - 矩阵不可变
设计 数组 矩阵 前缀和
中等
给定一个二维矩阵 matrix,以下类型的多个请求:
计算其子矩形范围内元素的总和,该子矩阵的 左上角 为 (row1, col1) ,右下角 为 (row2, col2) 。
实现 NumMatrix 类:
NumMatrix(int[][] matrix) 给定整数矩阵 matrix 进行初始化
int sumRegion(int row1, int col1, int row2, int col2) 返回 左上角 (row1, col1) 、右下角 (row2, col2) 所描述的子矩阵的元素 总和 。
示例 1:
输入:
["NumMatrix","sumRegion","sumRegion","sumRegion"]
[[[[3,0,1,4,2],[5,6,3,2,1],[1,2,0,1,5],[4,1,0,1,7],[1,0,3,0,5]]],[2,1,4,3],[1,1,2,2],[1,2,2,4]]
输出:
[null, 8, 11, 12]
解释:
NumMatrix numMatrix = new NumMatrix([[3,0,1,4,2],[5,6,3,2,1],[1,2,0,1,5],[4,1,0,1,7],[1,0,3,0,5]]);
numMatrix.sumRegion(2, 1, 4, 3); // return 8 (红色矩形框的元素总和)
numMatrix.sumRegion(1, 1, 2, 2); // return 11 (绿色矩形框的元素总和)
numMatrix.sumRegion(1, 2, 2, 4); // return 12 (蓝色矩形框的元素总和)
提示:
m == matrix.length
n == matrix[i].length
1 <= m, n <= 200
-105 <= matrix[i][j] <= 105
0 <= row1 <= row2 < m
0 <= col1 <= col2 < n
最多调用 104 次 sumRegion 方法
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/range-sum-query-2d-immutable
"""
from typing import List
class NumMatrix:
def __init__(self, matrix: List[List[int]]):
row_size, col_size = len(matrix), len(matrix[0]) if matrix else 0
sums = [[0] * (col_size + 1) for _ in range(row_size + 1)]
for i in range(row_size):
for j in range(col_size):
sums[i + 1][j + 1] = sums[i][j + 1] + sums[i + 1][j] - sums[i][j] + matrix[i][j]
self.sums = sums
def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
sums = self.sums
return sums[row2 + 1][col2 + 1] - sums[row1][col2 + 1] - sums[row2 + 1][col1] + sums[row1][col1]
if __name__ == '__main__':
nm = NumMatrix([[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]])
print(nm.sumRegion(2, 1, 4, 3))
assert nm.sumRegion(2, 1, 4, 3) == 8
print(nm.sumRegion(1, 1, 2, 2))
assert nm.sumRegion(1, 1, 2, 2) == 11
print(nm.sumRegion(1, 2, 2, 4))
assert nm.sumRegion(1, 2, 2, 4) == 12