stockSpan.cpp

//https://practice.geeksforgeeks.org/problems/stock-span-problem-1587115621/1

class Solution
{
    public:
    //Function to calculate the span of stock’s price for all n days.
    vector <int> calculateSpan(int price[], int n)
    {
       stack<pair<int, int>> s;
       vector<int> ans;
       
       for(int i=0; i<n; i++)
       {
           if(s.size()==0)
           {
               ans.push_back(-1);
           }
           else if(s.top().first > price[i] and s.size()>0)
           {
               ans.push_back(s.top().second);
           }
           else if(s.size()>0 and s.top().first<=price[i])
           {
               while(s.size()>0 and s.top().first <= price[i])
                s.pop();
                
                if(s.size()==0)
                {
                    ans.push_back(-1);
                }
                else
                {
                    ans.push_back(s.top().second);
                }
           }
           
           s.push({price[i], i});
       }
       
       for(int i=0;i<n;i++)
       {
           ans[i]=i-ans[i];
       }
       return ans;
    }
};