Coder's Legacy problem 2 WA

Someone please explain me that in the following codes, the first one gave me a wrong answer while the second one gave me an AC. Both the programs are ditto same in logic but i guess i am going wrong somewhere in the concept of vectors.
Please help…

  1. https://www.codechef.com/viewsolution/35686600
  2. https://www.codechef.com/viewsolution/35690548

https://www.codechef.com/viewsolution/35691734

This is completely your solution i just added if(k!=n ) because lower might get equal to v.end().
v.end()-v.begin() equals n… Now it didn’t throw RE as a[n] is returning some random value. Note the original vector has no number in nth position.

The first approach shows wrong verdict because when lower points to a.end(), then the value of k is n and a[n] contains garbage value and there may be an input in which sum of x and y is equal to that garbage value.
Look at this.
Same case does not occur with the second approach beacause in array a[n] = 0.

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You should rename the title of your post. It seems as if there was some issue with the problem.

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isn’t he doing the same in second code?

your first submission is contest submission, but second is after constest submission. they sometime change test cases in between.

but for vector a[n] is giving 0,its not throwing any runtime error

Ok, i think i got it.
Thanks a lot!!