I have observed that at most times, the difficulty for a problem in a problem set is different from its difficulty in the scoring distribution during the announcement of the contest. Does anybody know how is it calculated and why it takes so much time to get it updated, sometimes weeks?

P.S. I think that scoring distribution is just for the relative difficulty of the questions that will appear in the contest and problem set difficulty is just a different concept but still, I want to know, how are they calculated and what takes them so long to get updated. Thanks!

Is it possible to solve this problem in O(n) given that the numbers can only be in the range from 1 to 1000?

P.S: I tried solving this in O(n) but I am getting WA. I also created a random input generator and compared my output with the correct code for n = 100 and values from 1 to 100 but didn't find any difference.

int longestSubsequence(int N, int arr[])
{
    int dp[1002] = {0}; 

    int temp;
    for(int i = 1; i <= N; i++){
        temp = max(dp[arr[i - 1] - 1], dp[arr[i - 1] + 1]) + 1;
        dp[arr[i - 1]] = max(dp[arr[i - 1]], temp);
    }

    int mx = 0;
    for(int i = 0; i <= 1000; i++){
        mx = max(mx, dp[i]);
    }

    return mx;
}

Hello everybody,

I didn't completely understand the tutorial of Codeforces Round #649 Problem 1364A -XXXXX. Particularly, I am having trouble with this line of the tutorial. "So let the first non-multiple of x be at index l, and the last one be at index r. We must either remove the prefix all the way up to l or the suffix all the way up to r, and we'll clearly remove whichever shorter."

Could somebody please help me? I am new to codeforces and I really need help.