Longest Increasing Continuous Subsequence

Question

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.
Tags
Enumeration Dynamic Programming Array
Related Problems
Hard Longest Increasing Continuous subsequence II

Analysis

很直观的思路就是进行两次遍历,第一次从左到右,第二次从右往左,总是检查当前序列是否单调递增,并且记录当前最长的上升序列长度。
Check out the follow up question: Longest Increasing Continuous subsequence II

Solution

public class Solution {
/**
* @param A an array of Integer
* @return an integer
*/
public int longestIncreasingContinuousSubsequence(int[] A) {
if (A == null || A.length == 0) {
return 0;
}
int ans = 1;
int N = A.length;
// From left to right
int len = 1;
for (int i = 1; i < N; i++) {
if (A[i] > A[i - 1]) {
len++;
} else {
len = 1;
}
ans = Math.max(len, ans);
}
// From right to left
len = 1;
for (int i = N - 1; i > 0; i--) {
if (A[i - 1] > A[i]) {
len++;
} else {
len = 1;
}
ans = Math.max(len, ans);
}
return ans;
}
}