LeetCode 1762. Buildings With an Ocean View

原题链接在这里：https://leetcode.com/problems/buildings-with-an-ocean-view/description/
题目：

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.

Constraints:

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

题解：

Traverse from right to left.
Whenever encoutner a bigger value, we find an ocean view and update the maximum.

Time Complexity: O(n). n = heights.length.
Space: O(n).

AC Java:

class Solution {
    public int[] findBuildings(int[] heights) {
        List<Integer> res = new ArrayList<>();
        int n = heights.length;
        int max = 0;
        for(int i = n - 1; i >= 0; i--){
            if(heights[i] > max){
                max = heights[i];
                res.add(i);
            }
        }

        int[] resArr = new int[res.size()];
        for(int i = 0; i < res.size(); i++){
            resArr[res.size() - i - 1] = res.get(i);
        }

        return resArr;
    }
}

AC Python:

class Solution:
    def findBuildings(self, heights: List[int]) -> List[int]:
        res = []
        maxHeight = float('-inf')
        n = len(heights)

        for i in range(n - 1, -1, -1):
            if heights[i] > maxHeight:
                maxHeight = heights[i]
                res.append(i)
        
        return res[::-1]
        

类似Finding the Number of Visible Mountains.