503. Next Greater Element II 下一个更大元素

Posted 2020-10-19 Long Long Journey

 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. 

给定一个循环数组（最后一个元素的下一个元素是数组的第一个元素），为每个元素输出Next Greater Number。下一个更大数字x是数组中第一个更大的数字，这意味着您可以循环搜索以找到下一个更大的数字。如果不存在，则输出-1。

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var nextGreaterElements = function (nums) {
    let res = [];
    res.length = nums.length;
    res.fill(-1);
    let stack = [];
    let index = 0;
    while (index < nums.length * 2) {
        let cur = nums[index % nums.length];
        while (stack.length > 0 && nums[stack[stack.length - 1]] < cur) {
            res[stack.pop()] = cur;
        }
        if (index < nums.length) stack.push(index);
        index++
    }
    return res;
};
//let nums = [2, 1, 1, 3];
let nums = [1, 2, 1];
let res = nextGreaterElements(nums);
console.log(res);

来自为知笔记(Wiz)