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

1762. Buildings With an Ocean View
struct Solution;

impl Solution {
    fn find_buildings(heights: Vec<i32>) -> Vec<i32> {
        let mut stack = vec![];
        let n = heights.len();
        for i in 0..n {
            while let Some(&j) = stack.last() {
                if heights[j] <= heights[i] {
                    stack.pop();
                } else {
                    break;
                }
            }
            stack.push(i);
        }
        stack.into_iter().map(|i| i as i32).collect()
    }
}

#[test]
fn test() {
    let heights = vec![4, 2, 3, 1];
    let res = vec![0, 2, 3];
    assert_eq!(Solution::find_buildings(heights), res);
    let heights = vec![4, 3, 2, 1];
    let res = vec![0, 1, 2, 3];
    assert_eq!(Solution::find_buildings(heights), res);
    let heights = vec![2, 2, 2, 2];
    let res = vec![3];
    assert_eq!(Solution::find_buildings(heights), res);
}