503-下一个最大的数II

最新推荐文章于 2024-06-24 10:36:59 发布

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最新推荐文章于 2024-06-24 10:36:59 发布

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分类专栏：算法与数据结构 leetcode 文章标签：算法数据结构 leetcode

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本文介绍了一种解决环形数组下一个更大元素问题的方法。通过使用栈数据结构，该算法能够在O(n)的时间复杂度内找到每个元素的下一个更大元素，并返回相应的结果数组。

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Description

Given a circular array (the next element of the last element is the first element of the array), print the Next Greater Number for every element. The Next Greater Number of a number x is the first greater number to its traversing-order next in the array, which means you could search circularly to find its next greater number. If it doesn’t exist, output -1 for this number.

Example 1:

Input: [1,2,1]
Output: [2,-1,2]
Explanation: The first 1's next greater number is 2; 
The number 2 can't find next greater number; 
The second 1's next greater number needs to search circularly, which is also 2.

Note: The length of given array won’t exceed 10000.

问题描述

给定一个环形数组，输出数组中元素的下一个更大的元素(可以环形搜索)

解法

public class Solution {

    public int[] nextGreaterElements(int[] nums) {
        int[] res = new int[nums.length];
        Stack<Integer> stack = new Stack<>();

        for (int i = 2 * nums.length - 1; i >= 0; --i) {
            int temp = i % nums.length;
            while (!stack.empty() && stack.peek() <= nums[temp]) {
                stack.pop();
            }
            res[temp] = stack.empty() ? -1 : stack.peek();
            stack.push(nums[temp]);
        }

        return res;
    }
}