"""
Going from right to left
"""
class Solution:
    def findBuildings(self, heights: List[int]) -> List[int]:

        # tranverse from right to left
        index = len(heights)-1
        greatest_till_now = heights[-1]
        can_view = [len(heights)-1]

        for index in range(len(heights)-2, -1, -1):
            if heights[index] > greatest_till_now:
                greatest_till_now = heights[index]
                can_view.append(index)

        return  can_view[::-1]

"""
Going from left to right. Pop all previous buildings from the stack 
if they are shorter or equal to the current one (because they can no longer see the ocean).

Push the current building’s index onto the stack.
"""
class Solution:
    def findBuildings(self, heights: List[int]) -> List[int]:
        
        stack = []
        for i in range(len(heights)):
            # Pop all previous buildings from the stack 
            # if they are shorter or equal to the current one  
            while stack and heights[stack[-1]] <= heights[i]:
                stack.pop()
            stack.append(i)

        return stack