Description
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 <= 10^5
1 <= heights[i] <= 10^9
Solution
Iterate from right to left, only push those taller than top element into the stack.
Time complexity: o ( n ) o(n) o(n)
Space complexity: o ( n ) o(n) o(n)
Code
python3
class Solution:
def findBuildings(self, heights: List[int]) -> List[int]:
stack = []
for i in range(len(heights) - 1, -1, -1):
if not stack or heights[stack[-1]] < heights[i]:
stack.append(i)
return stack[::-1]