Next Greater Element II – LeetCode Solution Java , Python 3, Python 2 , C , C++, Best and Optimal Solutions , All you need.

Given a circular integer array nums (i.e., the next element of nums[nums.length - 1] is nums[0]), return the next greater number for every element in nums.

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, return -1 for this number.

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]

Constraints:

• 1 <= nums.length <= 104
• -109 <= nums[i] <= 109

C++ Next Greater Element II LeetCode Solution

  vector<int> nextGreaterElements(vector<int>& A) {
        int n = A.size();
        vector<int> stack, res(n, -1);
        for (int i = 0; i < n * 2; ++i) {
            while (stack.size() && A[stack.back()] < A[i % n]) {
                res[stack.back()] = A[i % n];
                stack.pop_back();
            }
            stack.push_back(i % n);
        }
        return res;
    }

Java Next Greater Element II LeetCode Solution

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

Python 3 Next Greater Element II LeetCode Solution

 def nextGreaterElements(self, A):
        stack, res = [], [-1] * len(A)
        for i in range(len(A)) * 2:
            while stack and (A[stack[-1]] < A[i]):
                res[stack.pop()] = A[i]
            stack.append(i)
        return res

Array-1180
String-562
Hash Table-412
Dynamic Programming-390
Math-368
Sorting-264

Greedy-257
Depth-First Search-256
Database-215
Breadth-First Search-200
Tree-195

Binary Search-191
Matrix-176
Binary Tree-160
Two Pointers-151
Bit Manipulation-140

Stack-133
Heap (Priority Queue)-117
Design-116
Graph-108
Simulation-103
Prefix Sum-96

Backtracking-92
Counting-86
Sliding Window-73
Linked List-69
Union Find-66

Ordered Set-48
Monotonic Stack-47
Recursion-43
Trie-41
Binary Search Tree-40
Divide and Conquer-40

Enumeration-39
Bitmask-37
Queue-33
Memoization-32
Topological Sort-31

Geometry-30
Segment Tree-27
Game Theory-24
Hash Function-24
Binary Indexed Tree-21

Interactive-18
Data Stream-17
String Matching-17
Rolling Hash-17
Shortest Path-16

Number Theory-16
Combinatorics-15
Randomized-12
Monotonic Queue-9
Iterator-9
Merge Sort-9

Concurrency-9
Doubly-Linked List-8
Brainteaser-8
Probability and Statistics-7
Quickselect-7

Bucket Sort-6
Suffix Array-6
Minimum Spanning Tree-5
Counting Sort-5
Shell-4

Line Sweep-4
Reservoir Sampling-4
Eulerian Circuit-3
Radix Sort-3

Strongly Connected Componen-t2
Rejection Sampling-2
Biconnected Component-1

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