#304

Range Sum Query 2D - Immutable

specialist · 750 · lc medium +31 · 57.9% accepted · 5,379 likes · top 54%

Description

Given a 2D integer matrix, answer repeated rectangular region sum queries.

Implement the NumMatrix class:

- NumMatrix(int[][] matrix) Initializes the object with the integer matrix matrix.

- int sumRegion(int row1, int col1, int row2, int col2) Returns the sum of all elements inside the rectangle whose upper left corner is (row1, col1) and lower right corner is (row2, col2).

You must design an algorithm where sumRegion works on O(1) time complexity.

Example 1:

Input

["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]]

Output

[null, 8, 11, 12]

Example 2:

Explanation

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 (i.e sum of the red rectangle)

numMatrix.sumRegion(1, 1, 2, 2); // return 11 (i.e sum of the green rectangle)

numMatrix.sumRegion(1, 2, 2, 4); // return 12 (i.e sum of the blue rectangle)

Code

class NumMatrix:

    def __init__(self, matrix: List[List[int]]):
        

    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
        


# Your NumMatrix object will be instantiated and called as such:
# obj = NumMatrix(matrix)
# param_1 = obj.sumRegion(row1,col1,row2,col2)

class NumMatrix:

    def __init__(self, matrix: List[List[int]]):
        

    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
        


# Your NumMatrix object will be instantiated and called as such:
# obj = NumMatrix(matrix)
# param_1 = obj.sumRegion(row1,col1,row2,col2)