Why My NNLog(N) soln got tle for 3rd Q , When N= 1000 , It should work , https://leetcode.com/problems/smallest-substring-with-identical-characters-i/solutions/6172861/need-help-why-2-n-n-log-n-solution-not-passed/ , Can anybody help.

Here , u just have to take a = c^d ,Then check if it do satisy the condition or not , if it doesn't then cout -1 , else cout a.

Proof: In my solution (283677605) you only ever add a bit to a if exactly one of c and d contains that bit, otherwise you either get a contradiction on the spot, or you don't add the bit and move on

why is that If you add that bit to a then (looking just at that bit) a | b=1 and so 1−c=d . If you don't add that bit, then a & c=0 and so b=d . If neither b=d nor c ^ d=1 holds then you can't construct such a . Note that carrying over never happens throughout the process.

. You can skip the latter cases and check if that value of a works, at the end. This is exactly equivalent to setting a=c ^ d and checking if it works.

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