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LeetCode376.java
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60 lines (57 loc) · 1.89 KB
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package problems;
public class LeetCode376 {
public static int wiggleMaxLength(int[] nums) {
int n = nums.length;
if(n < 2) {
return n;
}
int preDiff = nums[1] - nums[0];
int count = preDiff != 0 ? 2 : 0;
for (int i = 2; i < n; i++) {
int diff = nums[i] - nums[i - 1];
if((diff > 0 && preDiff <= 0) || (diff < 0 && preDiff >= 0)) {
count++;
preDiff = diff;
}
}
return count;
}
public static void main(String[] args) {
wiggleMaxLength(new int[]{3, 3, 3, 2, 5});
}
}
class LeetCode376_1{
/**
* up[i] 表示以前 i 个元素中的某一个为结尾的最长的「上升摆动序列」的长度。
* down[i] 表示以前 i 个元素中的某一个为结尾的最长的「下降摆动序列」的长度。
* 最终的状态转移方程：
* up[i] = up[i-1] if(nums[i] <= nums[i-1])
* max(up[i-1], down[i-1]+1) if(nums[i] > nums[i-1])
* down[i] = down[i-1] if(nums[i] >= nums[i-1])
* max(up[i-1]+1, down[i-1]) if(nums[i] < nums[i-1])
* @param nums
* @return
*/
public int wiggleMaxLength(int[] nums) {
int n = nums.length;
if(n < 2) {
return n;
}
int[] up = new int[n];
int[] down = new int[n];
up[0] = down[0] = 1;
for (int i = 1; i < n; i++) {
if(nums[i] > nums[i - 1]) {
up[i] = Math.max(up[i - 1], down[i - 1] + 1);
down[i] = down[i - 1];
} else if(nums[i] < nums[i - 1]) {
up[i] = up[i - 1];
down[i] = Math.max(up[i - 1] + 1, down[i - 1]);
} else {
up[i] = up[i - 1];
down[i] = down[i - 1];
}
}
return Math.max(up[n - 1], down[n - 1]);
}
}