kitesho's blog

By kitesho, 9 months ago, In English

You are given an array A of size N. For each prefix of the A, you have to calculate the value described in the below function.

int func(){
    int ans = 0;
    for(int i = 0; i <= prefix_index; i++){
        int c = 0;
        for(int j = 0; j <= prefix_index; j++){
              if(A[j] >= A[i]) c++;
        }
        ans = max(c * A[i], ans);
    }
    return ans;
}

i.e., in a prefix, the value for the index i is, number of elements greater than or equal to A[i] * A[i]. The answer for the prefix is maximum of these values. The output is a list of N numbers (one for each prefix).

constraints:
1 <= N <= 150000
1 <= A[i] <= 1e9

sample test case:
A = [10, 11, 12, 10, 11, 50, 70]
ans: [10, 20, 30, 40, 50, 60, 100]

test case explanation

I believe this can be solved using segment tree. Solutions without using segment tree will be also interesting. But want to know how to solve using segment tree.

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