Usage of map doubt

#1

Can u explain why we are using map in this case?

#2

hello @vatsal50

we want to store the prefix sum along with the index at which that particular sum occured thats why we are using map.
map[key]=value
key is prefix sum
value is the index at which the prefix sum occured.

using this map we can easy find the subarray with sum 0.
how?
let say prefsum is occured at index i and again occured at index j.
then this means subarray between [i+1…j] has sum zero becuase then ony it is possible to get the same prefsum back

#3

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