Given an unsorted array of integers, find the length of longest continuous increasing subsequence.
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.
这题挺好的,我想到两种方法,一种brute force,O(n2)不好;另一种,看到LIS就思维定势地想到了DP。
DP:
我写的leetcode submissions没保存,摘抄一个别人的:
public int findLengthOfLCIS(int[] nums) { if (nums == null || nums.length == 0) return 0; int n = nums.length; int[] dp = new int[n]; int max = 1; dp[0] = 1; for (int i = 1; i < n; i++) { if (nums[i] > nums[i - 1]) { dp[i] = dp[i - 1] + 1; } else { dp[i] = 1; } max = Math.max(max, dp[i]); } return max; }复制代码
但其实这题有更好的方法,
public int findLengthOfLCIS(int[] nums) { int res = 0, cnt = 0; for(int i = 0; i < nums.length; i++){ if(i == 0 || nums[i-1] < nums[i]) res = Math.max(res, ++cnt); else cnt = 1; } return res; }复制代码
用O(1)记录某个值然后随着滚动而重置,这种思想。