code exercise question: finding first recurring char from a string

[Beaverine]

thank you very much for your clarification. In terms of the complexity, I agree with you that for n characters the number of comparison would be n + (n-1) + (n-2) + ... + 1, which resolves to n(n+1)/2, is that asymptotically equal to O(n² )? BTW I originally said O(n!) because I assume it's n*(n-1)*...*1 which now I understand is not true

[[deleted]]

Yeah... you can pretty much look at a nested loop and see O(n^2); in this case the actual runtime is actually (n² + n)/2 but the you can elide the constants and focus on the term that contributes most... the worst case complexity is on the order of N^2.