300. Longest Increasing Subsequence

Posted 2021-01-25 jtechroad

// O(nlogn)
class Solution {
public:
    int lengthOfLIS(vector<int>& nums) {
        int n = nums.size(); if (n < 1) return 0;
        vector<int> dp;
        dp.push_back(nums[0]);
        for (int i = 1; i < n; i++) {
            auto p = lower_bound(dp.begin(), dp.end(), nums[i]);
            if (p == dp.end())
                dp.push_back(nums[i]);
            else
                *p = nums[i];
        }
        return dp.size();
    }
};
/*
// O(n*n)
class Solution {
public:
    int lengthOfLIS(vector<int>& nums) {
        int n = nums.size(); if (n < 1) return 0;
        vector<int> dp(n, 1);
        int res = 1;
        for (int i = 1; i < n; i++) {
            for (int j = 0; j < i; j++)
                if (nums[i] > nums[j])
                    dp[i] = max(dp[i], dp[j] + 1);
            res = max(res, dp[i]);
        }
        return res;
    }
};
*/