376. Wiggle Subsequence

不定期更新leetcode解题java答案。

采用pick one的方式选择题目。

题意为给定数组,获取满足要求的最长子串的长度。要求为前后两个数字差为绝对的正负关系(差为0不满足要求)。

例如,[1,7,4,9,2,5] is a wiggle sequence because the differences (6,-3,5,-7,3) 。

7-1=6>0, 4-7=-3<0, 9-4=5>0, 2-9=-7<0, 5-2=3>0。

采用贪心算法先获取两相邻数的差,再进行判断是否满足正负关系。试想若两个连续的差均为大于0的数,例如[2,1,3,5,...],则选取的留下数组有[2,1,3,...]和[2,1,5,...]。

显然后者更佳(容易满足题意),由此可得出如下代码:

 1 public class Solution {
 2     public int wiggleMaxLength(int[] nums) {
 3         if(nums.length == 0)
 4             return 0;
 5
 6         int[] differences = new int[nums.length - 1];
 7
 8         for(int i = 0; i < differences.length; i++)
 9             differences[i] = nums[i + 1] - nums[i];
10
11         int count = 1;
12         int lastValue = 0;
13         int difference = 0;
14         for(int i = 0; i < differences.length; i++){
15             difference = differences[i];   //get difference value
16
17             if(lastValue == 0){
18                 if(difference != 0){
19                     lastValue = difference > 0 ? 1 : -1;
20                     count++;
21                 }
22             }else{
23                 if(difference * lastValue < 0){
24                     lastValue = lastValue > 0 ? -1 : 1;
25                     count++;
26                 }
27             }
28         }
29
30         return count;
31     }
32 }
时间: 2024-10-27 06:04:34

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