2865. Beautiful Towers I

You are given a 0-indexed array maxHeights of n integers.

You are tasked with building n towers in the coordinate line. The ith tower is built at coordinate i and has a height of heights[i].

A configuration of towers is beautiful if the following conditions hold:

1. 1 <= heights[i] <= maxHeights[i]
2. heights is a mountain array.

Array heights is a mountain if there exists an index i such that:

• For all 0 < j <= i, heights[j - 1] <= heights[j]
• For all i <= k < n - 1, heights[k + 1] <= heights[k]

Return the maximum possible sum of heights of a beautiful configuration of towers.

class Solution {
public:
    long long maximumSumOfHeights(vector<int>& A) {
        int n = A.size();
        long long res = 0;
        auto left = [&](long long best, int p) {
            long long res = 0;
            for(int i = p; i >= 0; i--) {
                best = min(best, 1ll * A[i]);
                res += best;
            }
            return res;
        };
        auto right = [&](long long best, int p) {
            long long res = 0;
            for(int i = p; i < n; i++) {
                best = min(best, 1ll * A[i]);
                res += best;
            }
            return res;
        };
        for(int i = 0; i < n; i++) {
            res = max(res, A[i] + left(A[i],i-1) + right(A[i],i+1));
        }
        return res;
    }
};