1762. Buildings With an Ocean View

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

Solution1:

class Solution(object):
    def findBuildings(self, heights):
        """
        :type heights: List[int]
        :rtype: List[int]
        """
        if not heights:
            return []
        
        output = [len(heights)-1]
        j = len(heights)-2
        largest = heights[-1]
        
        while j >= 0:
            if heights[j] > largest:
                output.append(j)
                largest = heights[j]
            j -= 1
            
        return output[::-1]
        

Solution2:

class Solution:
    def findBuildings(self, heights):
        
        answer = []
        maxHeight = 0
        
        for i in range(len(heights) - 1, -1, -1):
            if heights[i] > maxHeight:
                answer.append(i)
                maxHeight = heights[i]
                
        return reversed(answer)

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