LeetCode-in-All
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
import "math"
func lengthOfLIS(nums []int) int {
if nums == nil || len(nums) == 0 {
return 0
}
dp := make([]int, len(nums)+1)
for i := 1; i < len(dp); i++ {
dp[i] = math.MaxInt64
}
left, right := 1, 1
for _, curr := range nums {
start, end := left, right
for start+1 < end {
mid := start + (end-start)/2
if dp[mid] > curr {
end = mid
} else {
start = mid
}
}
if dp[start] > curr {
dp[start] = curr
} else if curr > dp[start] && curr < dp[end] {
dp[end] = curr
} else if curr > dp[end] {
dp[end+1] = curr
right++
}
}
return right
}