find peak or drop

最新推荐文章于 2025-01-05 22:45:00 发布

sjphiChina

最新推荐文章于 2025-01-05 22:45:00 发布

阅读量391

点赞数

CC 4.0 BY-SA版权

分类专栏： strStr 队列

本文链接：https://blog.youkuaiyun.com/sjphiChina/article/details/52411032

strStr 同时被 2 个专栏收录

360 篇文章

订阅专栏

队列

63 篇文章

订阅专栏

本文介绍了一种改进的寻峰填谷算法实现，通过迭代而非递归方式寻找数组中的峰值或谷值元素。该算法适用于包含峰值和谷值变化的数据序列，并提供了几个测试案例以验证其正确性和效率。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

//http://www.1point3acres.com/bbs/forum.php?mod=viewthread&tid=156077&extra=page%3D2%26filter%3Dsortid%26sortid%3D311%26searchoption%5B3046%5D%5Bvalue%5D%3D2%26searchoption%5B3046%5D%5Btype%5D%3Dradio%26sortid%3D311
找打peak or drop，原来用的是递归，这次改为迭代

public static int helper1(int[] nums) {
	    if (nums.length == 0)
            return -1;
        int len = nums.length;
        if (Math.abs(nums[len - 1] - nums[0]) == len - 1)
            return -1;// There is no such a valley or peak
        int start = 0, end = nums.length - 1;
        while (start < end) {
            int mid = start + (end - start) / 2;
            if ((nums[mid - 1] - nums[mid]) * (nums[mid + 1] - nums[mid]) > 0)
                return nums[mid];
            int diffOfIndex = mid - start;
            int diffOfValue = Math.abs(nums[mid] - nums[start]);
            //因为如果不相差，则下标和值是对应的，则没有发生波峰或波谷
            if (diffOfIndex == diffOfValue)
                start = mid;
            else
                end = mid;
        }
        return -1;
	}
	

	public static void main(String[] args) {
		int[] nums1 = { 1, 2, 3, 4, 3, 2 };
		int[] nums2 = {};
		int[] nums3 = { 1, 2, 3, 4, 5, 6, 7, 8, 7 };
		int[] nums4 = { 1, 2, 3, 4, 5 };
		int[] nums5 = { 5, 4, 3, 2, 1, 2, 3 };
		int[] nums6 = { 9, 8, 7, 6, 7 };
		System.out.println(find(nums1));
		System.out.println(find(nums2));
		System.out.println(find(nums3));
		System.out.println(find(nums4));
		System.out.println(find(nums5));
		System.out.println(find(nums6));
		System.out.println(helper1(nums1));
        System.out.println(helper1(nums2));
        System.out.println(helper1(nums3));
        System.out.println(helper1(nums4));
        System.out.println(helper1(nums5));
        System.out.println(helper1(nums6));
	}