CAnt understand initial constraints

#1

Kindly help me understanding

#2

Hey in the section you raised doubt, I can only see the editorial video. In that they are not talking about any constraints. Please raise the doubt in relevant section.
I would explain once what they are doing in the video, our aim is to find the longest subarray with sum 0. Now we take prefix sum of the array, and try to find if the we have current sum before or not, cause if we have encountered the same sum before it means that the sum of subarray in-between these two values is zero.
Eg suppose pref[i]=a, pref[j]=a, this means sum(a[i+1],…a[j])=0.

#3

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