I know time complexity give us an idea of the execution time of an algorithm.But in contests,what is this necessary for? Do programmers use it for something?Some problems have notations such " O(n3) ". Do they use it for calculate something before they start implementing the solution,I mean before start coding?

PROBLEM -> https://codeforces.me/problemset/problem/1389/C

I have been trying to solve this problem and my logic to try achieve that was:

Compare the Left Cyclic Array with the Right Cyclic Array.If both are equal,the array is good.If it doesn't check if the numbers of the input array are different.If they are,subtract the length by 2,because a good array would be a combination of just 2 items of them,such:

95381 -> 51

If there is a number duplicated in the input array,such (1,1,2,3,4,5); Count the number of occurrences of the most frequent number.Use this to subtract from array length. Example:(1,1,1,1,2,3);(4 occurences of the number "1") A Good String would be: 1111 . Array length = 6 => 6(length)-4(occurrences)="2".

In the first test,it worked.But in the second not. You can see my last submission in PHP: https://codeforces.me/submissions/luizantonioprg Is my logic wrong?