https://leetcode.com/problems/next-greater-element-ii/

Example 1:

Input: nums = [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.

Example 2:

Input: nums = [1,2,3,4,3]
Output: [2,3,4,-1,4]

nums2 = nums拉長兩倍

初始化一個reuslt array，長度為nums，fill -1

初始化一個stack

for i, num in nums2

• while (stack’s length >0) & (num > nums[stack’s top])
  • top = stack.pop
  • result[top % len(nums)] = num
• push(i)

return result

func nextGreaterElements(nums []int) []int {

	nums2 := append(nums, nums...)

	result := make([]int, len(nums))

	for i := range result {
		result[i] = -1
	}

	stack := []int{}

	for i, num := range nums2 {

		for len(stack) > 0 && num > nums2[stack[len(stack)-1]] {

			top := stack[len(stack)-1]
			stack = stack[:len(stack)-1]
			result[top%len(nums)] = num

		}

		stack = append(stack, i)

	}

	return result

}