Next Greater Element II — Circular Array Monotonic Stack

# Python
def nextGreaterElements(nums):
    n = len(nums); res = [-1]*n; stack = []
    for i in range(2*n):
        while stack and nums[stack[-1]] < nums[i%n]:
            res[stack.pop()] = nums[i%n]
        if i < n: stack.append(i)
    return res

// Java
public int[] nextGreaterElements(int[] nums) {
    int n = nums.length; int[] res = new int[n]; Arrays.fill(res, -1);
    Deque<Integer> stack = new ArrayDeque<>();
    for (int i = 0; i < 2*n; i++) {
        while (!stack.isEmpty() && nums[stack.peek()] < nums[i%n])
            res[stack.pop()] = nums[i%n];
        if (i < n) stack.push(i);
    }
    return res;
}

// C++
vector<int> nextGreaterElements(vector<int>& nums) {
    int n = nums.size(); vector<int> res(n,-1); stack<int> st;
    for (int i = 0; i < 2*n; i++) {
        while (!st.empty() && nums[st.top()] < nums[i%n])
            res[st.top()]=nums[i%n], st.pop();
        if (i < n) st.push(i);
    }
    return res;
}