[williamkuszmaul]

Unless I'm misreading, the question as stated in the blog post never says there is only one duplicate (there might be many!), so in that sense I think his answer may be wrong. A more robust solution is just to have an array of n counters and just count how many times each item appears.

[philiiiiiipp]

> when given an array of length n + 1 containing integers 1 through n, find the duplicate integer in an array.

I do believe it is only one.

[jhot]

The length is n+1 and contains all ints 1 through n, so there can only be a single duplicate.

[williamkuszmaul]

But does the question ever say "all"...?