matrix-range-sum.py

# Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).

# Range Sum Query 2D
# The above rectangle (with the red border) is defined by (row1, col1) = (2, 1) and (row2, col2) = (4, 3), which contains sum = 8.

# Example:
# Given matrix = [
#   [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]
# ]

# sumRegion(2, 1, 4, 3) -> 8
# sumRegion(1, 1, 2, 2) -> 11
# sumRegion(1, 2, 2, 4) -> 12
# Note:
# You may assume that the matrix does not change.
# There are many calls to sumRegion function.
# You may assume that row1 ≤ row2 and col1 ≤ col2.
class NumMatrix(object):

    def __init__(self, matrix):
        """
        :type matrix: List[List[int]]
        """
        self.matrix=matrix
        

    def sumRegion(self, row1, col1, row2, col2):
        """
        :type row1: int
        :type col1: int
        :type row2: int
        :type col2: int
        :rtype: int
        """
        sum=0
        for x in range(row1,row2+1):
            for y in range(col1,col2+1):
                sum=sum+matrix[x][y]
        return sum

        


# Your NumMatrix object will be instantiated and called as such:
matrix = [
  [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]
]
obj = NumMatrix(matrix)
param_1 = obj.sumRegion(1,1,2,2)
print(param_1)