class NumMatrix(object):
def __init__(self, matrix):
"""
initialize your data structure here.
:type matrix: List[List[int]]
"""
if not matrix:
return
m, n = len(matrix), len(matrix[0])
self.__sums = [[0 for _ in xrange(n+1)] for _ in xrange(m+1)]
for i in xrange(1, m+1):
for j in xrange(1, n+1):
self.__sums[i][j] = self.__sums[i][j-1] + matrix[i-1][j-1]
for j in xrange(1, n+1):
for i in xrange(1, m+1):
self.__sums[i][j] += self.__sums[i-1][j]
def sumRegion(self, row1, col1, row2, col2):
"""
sum of elements matrix[(row1,col1)..(row2,col2)], inclusive.
:type row1: int
:type col1: int
:type row2: int
:type col2: int
:rtype: int
"""
return self.__sums[row2+1][col2+1] - self.__sums[row2+1][col1] - \
self.__sums[row1][col2+1] + self.__sums[row1][col1]
# Your NumMatrix object will be instantiated and called as such:
# numMatrix = NumMatrix(matrix)
# numMatrix.sumRegion(0, 1, 2, 3)
# numMatrix.sumRegion(1, 2, 3, 4)
304. Range Sum Query 2D - Immutable
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