LeetCode-503. Next Greater Element II [C++][Java]

LeetCode-503. Next Greater Element IIhttps://leetcode.com/problems/next-greater-element-ii/

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 <= 10^4
• -10^9 <= nums[i] <= 10^9

class Solution {
public:
    vector nextGreaterElements(vector& nums) {
        if (nums.empty()) {return {};}
        stack> bag;
        int size = nums.size();
        vector tmp(size, -1);
        bag.emplace(nums[0], 0);
        for(int i = 1; i < size; ++i) {
            while(!bag.empty() && bag.top().first < nums[i]) {
                tmp[bag.top().second] = nums[i];
                bag.pop();
            }
            bag.emplace(nums[i], i);
        }
        
        for(int i = 0; i < size - 1; ++i) {
            while(!bag.empty() && bag.top().first < nums[i]) {
                tmp[bag.top().second] = nums[i];
                bag.pop();
            }
        }
        return tmp;
    }
};

class Solution {
    public int[] nextGreaterElements(int[] nums) {
        if (nums == null || nums.length == 0) {return new int[]{};}
        Stack bag = new Stack<>();
        int size = nums.length;
        int[] tmp = new int[size];
        Arrays.fill(tmp, -1);
        bag.add(new int[]{nums[0], 0});
        for(int i = 1; i < size; ++i) {
            while(!bag.empty() && bag.peek()[0] < nums[i]) {
                tmp[bag.peek()[1]] = nums[i];
                bag.pop();
            }
            bag.add(new int[]{nums[i], i});
        }
        
        for(int i = 0; i < size - 1; ++i) {
            while(!bag.empty() && bag.peek()[0] < nums[i]) {
                tmp[bag.peek()[1]] = nums[i];
                bag.pop();
            }
        }
        return tmp;
    }
}