Leetcode300

Longest Increasing Subsequence:
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.

Solution:

#include 
#include 

using namespace std;

class Solution {
public:
    int lengthOfLIS(vector& nums) {

        if ( nums.size() == 0)
            return 0;

        // memo[i]表示以 nums[i] 为结尾的最长上升子序列的长度
        vector memo(nums.size(), 1);
        for (int i = 1; i < nums.size() ; i++) {
            for (int j = 0; j < i ; j++) {
                if ( nums[j] < nums[i] )
                    memo[i] = max(memo[i], 1+memo[j]);
            }
        }

        int res = 1;
        for (int i = 0; i < nums.size(); i++) {
            res = max(res, memo[i]);
        }

        return res;
    }
};

总结：看注释，“结尾”两字太妙了