1762

1762. Buildings With an Ocean View (Medium)

There are n buildings in a line. You are given an integer array heights of size n that represents the heights of the buildings in the line.

The ocean is to the right of the buildings. A building has an ocean view if the building can see the ocean without obstructions. Formally, a building has an ocean view if all the buildings to its right have a smaller height.

Return a list of indices (0-indexed) of buildings that have an ocean view, sorted in increasing order.

 

Example 1:

Input: heights = [4,2,3,1]
Output: [0,2,3]
Explanation: Building 1 (0-indexed) does not have an ocean view because building 2 is taller.

Example 2:

Input: heights = [4,3,2,1]
Output: [0,1,2,3]
Explanation: All the buildings have an ocean view.

Example 3:

Input: heights = [1,3,2,4]
Output: [3]
Explanation: Only building 3 has an ocean view.

Example 4:

Input: heights = [2,2,2,2]
Output: [3]
Explanation: Buildings cannot see the ocean if there are buildings of the same height to its right.

 

Constraints:

• 1 <= heights.length <= 105
• 1 <= heights[i] <= 109

Companies:
Facebook, Microsoft, Amazon

Related Topics:
Array, Stack, Monotonic Stack

Similar Questions:

• Number of Visible People in a Queue (Hard)

Solution 1.

// OJ: https://leetcode.com/problems/buildings-with-an-ocean-view/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    vector<int> findBuildings(vector<int>& A) {
        vector<int> ans{(int)A.size() - 1};
        for (int i = A.size() - 2; i >= 0; --i) {
            if (A[i] > A[ans.back()]) ans.push_back(i);
        }
        reverse(begin(ans), end(ans));
        return ans;
    }
};