JIAKAOBO

LeetCode

venmo
wechat

感谢赞助!

  • ㊗️
  • 大家
  • offer
  • 多多！

Problem

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

Code

class Solution {
    public int[] findBuildings(int[] heights) {
        Stack<Integer> stack = new Stack<>();
        List<Integer> res = new ArrayList<>();
        for(int i = heights.length - 1; i >=0; i--) {
            int height = heights[i];
            if(i == heights.length - 1){
                res.add(i);
                stack.push(height);
            } else {
                if(height < stack.peek()) continue;
                while(!stack.isEmpty() && height > stack.peek()) {
                    stack.pop();
                }

                stack.push(height);

                if(stack.size() == 1) res.add(i);
            }
        }

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

        return r;
    }
}