Package g1901_2000.s1964_find_the_longest_valid_obstacle_course_at_each_position

Class Solution

  • public class Solution
extends Object
    1964 - Find the Longest Valid Obstacle Course at Each Position.

    Hard

    You want to build some obstacle courses. You are given a 0-indexed integer array obstacles of length n, where obstacles[i] describes the height of the ith obstacle.

    For every index i between 0 and n - 1 ( inclusive ), find the length of the longest obstacle course in obstacles such that:

    • You choose any number of obstacles between 0 and i inclusive.
    • You must include the ith obstacle in the course.
    • You must put the chosen obstacles in the same order as they appear in obstacles.
    • Every obstacle (except the first) is taller than or the same height as the obstacle immediately before it.

    Return an array ans of length n, where ans[i] is the length of the longest obstacle course for index i as described above.

    Example 1:

    Input: obstacles = [1,2,3,2]

    Output: [1,2,3,3]

    Explanation: The longest valid obstacle course at each position is:

    • i = 0: [1], [1] has length 1.

    • i = 1: [1,2], [1,2] has length 2.

    • i = 2: [1,2,3], [1,2,3] has length 3.

    • i = 3: [1,2,3,2], [1,2,2] has length 3.

    Example 2:

    Input: obstacles = [2,2,1]

    Output: [1,2,1]

    Explanation: The longest valid obstacle course at each position is:

    • i = 0: [2], [2] has length 1.

    • i = 1: [2,2], [2,2] has length 2.

    • i = 2: [2,2,1], [1] has length 1.

    Example 3:

    Input: obstacles = [3,1,5,6,4,2]

    Output: [1,1,2,3,2,2]

    Explanation: The longest valid obstacle course at each position is:

    • i = 0: [3], [3] has length 1.

    • i = 1: [3,1], [1] has length 1.

    • i = 2: [3,1,5], [3,5] has length 2. [1,5] is also valid.

    • i = 3: [3,1,5,6], [3,5,6] has length 3. [1,5,6] is also valid.

    • i = 4: [3,1,5,6,4], [3,4] has length 2. [1,4] is also valid.

    • i = 5: [3,1,5,6,4,2], [1,2] has length 2.

    Constraints:

    • n == obstacles.length
    • 1 <= n <= 105
    • 1 <= obstacles[i] <= 107

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • longestObstacleCourseAtEachPosition

        public int[] longestObstacleCourseAtEachPosition​(int[] obstacles)