Why we write a-1 instead of a

#1

sir has wrote csum[b]-csum[a-1] insted of writing csum[a].Why?

#2

hi @swatantra1240_25a488bfc859a4ab,

for cummulative sum u need to write a-1 as u need sum from a to b eg array is 1,2,3,4,5 csum is 1,3,6,10,15 if u want sum from 2 to 4th index i.e 3+4+5 = 12 then u will do csum[4] - csum[2-1] => 15 - 3 = 12

#3

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