I have coded as per my understanding but all tc are getting failed and not able to detect problem in code.
Failing testcases
Check now ->
Passing all test cases.
Why we taking pre[0] =1 ?
You can ignore that, and make rest same. It will still work same.
No, it is not. Commenting that line will fail all testcases
Yes, it’s like for test case:
5 5 5 5 5
value of mod will be 0 every time. So total sum will be 5 in pre[0] if you are not keeping pre[0]=1. So if you don’t keep pre[0]=1 answer will be 5, but expected answer will be 6.
So if any sub-array sum from index i’th to j’th is divisible by k then we can say a[0]+…a[i-1] (mod n) = a[0]+…+a[j] (mod n)
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