Leetcode #300. Longest Increasing Subsequence

public class Solution {
    public int lengthOfLIS(int[] nums) {
        int[] dp =new int[nums.length];
        int max = 0;
        for(int i=0,len = nums.length;i<len;i++){
            dp[i]=1;
            for(int j=0;j<i;j++){
                if(nums[j]<nums[i])
                    dp[i] = Math.max(dp[j]+1,dp[i]);
            }
            max = Math.max(dp[i],max);
        }
        return max;
    }
}

从第一个开始检查，注意，并不是指连续的序列。详见题目：https://leetcode.com/problems/longest-increasing-subsequence/#/description
参考文章：http://www.hawstein.com/posts/dp-novice-to-advanced.html

follow up

334. Increasing Triplet Subsequence##

public class Solution {
    public boolean increasingTriplet(int[] nums) {
        int min = Integer.MAX_VALUE,sec_min = Integer.MAX_VALUE;
        for(int i:nums){
            if(i<=min) min = i;
            else if(i<=sec_min) sec_min = i;
            else return true;
        }
        return false;
    }
}

这题的关键是要维护一个最小值和次小值。