最长湍流子数组

/* 
 * 思路：
 * 使用流处理方法，首先创建一个差值数组diff，记录相邻元素的差值，然后根据差值正负交替的规则来计算最大湍流子数组的长度。
 */
import java.util.stream.IntStream;
public class Solution {
    public int maxTurbulenceSize(int[] arr) {
        if (arr.length == 1) return 1;
        int maxLen = 1;
        int increasing = 1, decreasing = 1;
        int[] diff = IntStream.range(1, arr.length)
                               .map(i -> Integer.compare(arr[i], arr[i - 1]))
                               .toArray();
        for (int i = 0; i < diff.length; i++) {
            if (diff[i] == 1) {
                increasing = decreasing + 1;
                decreasing = 1;
            } else if (diff[i] == -1) {
                decreasing = increasing + 1;
                increasing = 1;
            } else {
                increasing = 1;
                decreasing = 1;
            }
            maxLen = Math.max(maxLen, Math.max(increasing, decreasing));
        }
        return maxLen;
    }
}