/
2d-range-sum.py
28 lines (25 loc) · 1.11 KB
/
2d-range-sum.py
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import copy
class NumMatrix(object):
def __init__(self, matrix):
self.dp=copy.deepcopy(matrix)
for i in xrange(len(matrix)):
for j in xrange(len(matrix[0])):
if i==0 and j==0: continue
if i==0:
self.dp[i][j]+=self.dp[i][j-1]
continue
if j==0:
self.dp[i][j]+=self.dp[i-1][j]
continue
self.dp[i][j]+=self.dp[i][j-1]+self.dp[i-1][j]-self.dp[i-1][j-1]
print self.dp
def sumRegion(self, row1, col1, row2, col2):
if row1==0 and col1==0: return self.dp[row2][col2]
if row1==0: return self.dp[row2][col2]-self.dp[row2][col1-1]
if col1==0: return self.dp[row2][col2]-self.dp[row1-1][col2]
return self.dp[row2][col2]-self.dp[row1-1][col2]-self.dp[row2][col1-1]+self.dp[row1-1][col1-1]
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(0,0,0,0)
print nm.sumRegion(2, 1, 4, 3)# -> 8
print nm.sumRegion(1, 1, 2, 2)# -> 11
print nm.sumRegion(1, 2, 2, 4)# -> 12