LintCode Longest Increasing Continuous Subsequence

原题链接在这里：http://www.lintcode.com/en/problem/longest-increasing-continuous-subsequence/

题目：

Give an integer array，find the longest increasing continuous subsequence in this array.

An increasing continuous subsequence:

• Can be from right to left or from left to right.
• Indices of the integers in the subsequence should be continuous.

 Notice

O(n) time and O(1) extra space.

Example

For [5, 4, 2, 1, 3], the LICS is [5, 4, 2, 1], return 4.

For [5, 1, 2, 3, 4], the LICS is [1, 2, 3, 4], return 4.

题解：

从左向右 若连续递增 就更新 len, 再从右向左 若连续递增 就更新res.

Time Complexity: O(n). Space: O(1).

AC Java:

public class Solution {
    public int longestIncreasingContinuousSubsequence(int[] A) {
        if(A == null || A.length == 0){
            return 0;
        }
        
        int res = 1;
        int len = 1;
        for(int i = 1; i<A.length; i++){
            if(A[i] > A[i-1]){
                len++;
            }else{
                len = 1;
            }
            res = Math.max(res, len);
        }
        
        len = 1;
        for(int i = A.length-2; i>=0; i--){
            if(A[i] > A[i+1]){
                len++;
            }else{
                len = 1;
            }
            res = Math.max(res, len);
        }
        
        return res;
    }
}

 跟上Longest Increasing Continuous subsequence II.