循环解题：

class Solution {
public:vector<int> nextGreaterElements(vector<int>& nums) {int n = nums.size();vector<int> res;for (int i = 0; i <n; i++){int k = i;bool flag = false;for (int j = 1;j <=n-1;j++){if((k+j)%n != k && nums[(k+j)%n]>nums[i]) {res.push_back(nums[(k+j)%n]);flag = true;break;}}if (!flag) res.push_back(-1);}return res;}
};

下面开始理解，

方法一：单调栈+循环数组

class Solution {
public:vector<int> nextGreaterElements(vector<int>& nums) {int n = nums.size();vector<int> ret(n, -1);stack<int> stk;for (int i = 0; i < n * 2 - 1; i++) {while (!stk.empty() && nums[stk.top()] < nums[i % n]) {ret[stk.top()] = nums[i % n];stk.pop();}stk.push(i % n);}return ret;}
};

python

class Solution:def nextGreaterElements(self, nums: List[int]) -> List[int]:n = len(nums)ret = [-1] * nstk = list()for i in range(n*2 -1):while stk and nums[stk[-1]] < nums[i%n]:ret[stk.pop()] = nums[i%n]stk.append(i%n);return ret