Leetcode: Range Sum Query 2D - Mutable && Summary: Binary Indexed Tree
Givena2Dmatrixmatrix,findthesumoftheelementsinsidetherectangledefinedbyitsupperleftcorner(row1,col1)andlowerrightcorner(row2,col2).
RangeSumQuery2D
Theaboverectangle(withtheredborder)isdefinedby(r