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376. 摆动序列 - 力扣（LeetCode）

定义两个动态规划数组，一个记录上升的dp,一个记录下降的dp

如果后一位数大于前一位数，则有

dpUp[i] = dpDown[i - 1] + 1;
dpDown[i] = dpDown[i - 1];

如果后一位数小于前一位数，则有

dpUp[i] = dpUp[i - 1] ;
dpDown[i] = dpUp[i - 1]+ 1;

如果相等，则dp[i] = dp[i-1]

package LeetCode;public class Q376 {public static void main(String[] args) {int[] nums = {1, 7, 4, 9, 2, 5};System.out.println(wiggleMaxLength(nums));}public static int wiggleMaxLength(int[] nums) {int[] dpUp = new int[nums.length];int[] dpDown = new int[nums.length];dpUp[0] = 1;dpDown[0] = 1;for (int i = 1; i < nums.length; i++) {if (nums[i] - nums[i - 1] == 0) {dpUp[i] = dpUp[i - 1];dpDown[i] = dpDown[i - 1];} else if (nums[i] - nums[i - 1] > 0) {dpUp[i] = dpDown[i - 1] + 1;dpDown[i] = dpDown[i - 1];} else {dpUp[i] = dpUp[i - 1] ;dpDown[i] = dpUp[i - 1]+ 1;}}return Math.max(dpUp[dpUp.length-1],dpDown[dpDown.length-1]);}
}