leetcode 300. Longest Increasing Subsequence

Seawolf

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?

dp solution

class Solution {
public:
    int lengthOfLIS(vector<int>& nums) {
        if(nums.size() == 0) return 0;
        int dp[nums.size()] = {0};
        dp[0] = 1;
        int max_ans = 0;
        for(int i = 0; i < nums.size();i++){
            int max1 = 0;
            for(int j = 0; j < i; j++){
                if(nums[j] < nums[i]){
                    max1 = max(max1, dp[j]);
                }
            }
            
            dp[i] = max1 +1;
            max_ans = max(max_ans,dp[i]);
        }
        
        return max_ans;
    }
};