674. Longest Continuous Increasing Subsequence

Description

Given an unsorted array of integers, find the length of longest continuous increasing subsequence (subarray).

Example 1:
Input: [1,3,5,4,7]
Output: 3
Explanation: The longest continuous increasing subsequence is [1,3,5], its length is 3.
Even though [1,3,5,7] is also an increasing subsequence, it's not a continuous one where 5 and 7 are separated by 4.

Example 2:
Input: [2,2,2,2,2]
Output: 1
Explanation: The longest continuous increasing subsequence is [2], its length is 1.

Note: Length of the array will not exceed 10,000.

Solution

DP, time O(n), space O(1)

很简单的DP问题。

class Solution {
    public int findLengthOfLCIS(int[] nums) {
        if (nums == null || nums.length == 0) {
            return 0;
        }
        
        int lcisLength = 1;
        int preLength = 1;
        
        for (int i = 1; i < nums.length; ++i) {
            if (nums[i] > nums[i - 1]) {
                lcisLength = Math.max(lcisLength, ++preLength);
            } else {
                preLength = 1;
            }
        }
        
        return lcisLength;
    }
}