LeetCode-in-Swift
300. Longest Increasing Subsequence
Medium
Given an integer array nums, return the length of the longest strictly increasing subsequence.
A subsequence is a sequence that can be derived from an array by deleting some or no elements without changing the order of the remaining elements. For example, [3,6,2,7] is a subsequence of the array [0,3,1,6,2,2,7].
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 {
func lengthOfLIS(_ nums: [Int]) -> Int {
if nums.isEmpty {
return 0
}
var dp = [Int](repeating: Int.max, count: nums.count + 1)
dp[0] = Int.min
var length = 0
for num in nums {
var left = 0
var right = length
while left <= right {
let mid = left + (right - left) / 2
if dp[mid] < num {
left = mid + 1
} else {
right = mid - 1
}
}
dp[left] = num
if left > length {
length = left
}
}
return length
}
}