496. Next Greater Element I

https://leetcode.com/problems/next-greater-element-i/description/

class Solution {
public:
    vector<int> nextGreaterElement(vector<int>& findNums, vector<int>& nums) {
        unordered_map<int,int> m;
        stack<int> st;
        for (int i = nums.size() - 1; i >= 0; i--) {
            int cur = nums[i];
            while (!st.empty() && cur >= st.top())
                st.pop();
            if (st.empty())
                m[cur] = -1;
            else
                m[cur] = st.top();
            st.push(cur);
        }
        
        vector<int> res;
        for (auto i : findNums)
            res.push_back(m[i]);
        return res;
    }
};