300. Longest Increasing Subsequence¶

LeetCode Problem View on GitHub

300. Longest Increasing Subsequence

Medium

Given an integer array nums, return the length of the longest strictly increasing subsequence.

Example 1:

Input: nums = [10,9,2,5,3,7,101,18]
Output: 4
Explanation: The longest increasing subsequence is [2,3,7,101], therefore the length is 4.

Example 2:

Input: nums = [0,1,0,3,2,3]
Output: 4

Example 3:

Input: nums = [7,7,7,7,7,7,7]
Output: 1

Constraints:

• 1 <= nums.length <= 2500
• -104 <= nums[i] <= 104

Follow up: Can you come up with an algorithm that runs in O(n log(n)) time complexity?

Solution¶

class Solution {
    public int lengthOfLIS(int[] nums) {
        int n = nums.length;
        TreeSet<Integer> set = new TreeSet<>();
        for (int i = 0; i < n; i++) {
            int current = nums[i];
            if (set.contains(current)) continue;
            Integer next = set.higher(current);
            if (next != null) {
                set.remove(next);
                set.add(current);
            }
            else set.add(current);
        }
        return set.size();
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here