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longestIncreasingSubsequence.swift
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/*
Given an unsorted array of integers, find the length of longest increasing subsequence.
Example:
Input: [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.
Note:
* There may be more than one LIS combination, it is only necessary for you to return the length.
* Your algorithm should run in O(n2) complexity.
Follow up: Could you improve it to O(n log n) time complexity?
https://leetcode.com/problems/longest-increasing-subsequence/
*/
func lengthOfLIS(_ nums: [Int]) -> Int {
guard nums.count > 1 else { return nums.count }
var dp = [[Int]]()
dp.append([nums[0]])
var longest = 1
for i in 1..<nums.count {
var maxCount = 0
var maxIndex = 0
for j in 0..<i {
if nums[i] > nums[j] {
if dp[j].count > maxCount {
maxCount = dp[j].count
maxIndex = j
}
}
}
// smallest so far, just append
if maxCount == 0 {
dp.append([nums[i]])
} else {
var list = dp[maxIndex]
list.append(nums[i])
if list.count > longest { longest = list.count }
dp.append(list)
}
}
return longest
}