304. Range Sum Query 2D - Immutable

class NumMatrix:
    '''
    DP

    '''
    def __init__(self, matrix: List[List[int]]):
        M, N = len(matrix), len(matrix) and len(matrix[0])
        self.AGG = [[0] * (N+1) for _ in range(M+1)]
        for i in range(M):
            for j in range(N):
                self.AGG[i+1][j+1] = matrix[i][j] + self.AGG[i][j+1] + self.AGG[i+1][j] - self.AGG[i][j]

    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
        return self.AGG[row2+1][col2+1] + self.AGG[row1][col1] - self.AGG[row1][col2+1] - self.AGG[row2+1][col1]

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

mengyushi / LeetCode

304. Range Sum Query 2D - Immutable #261