Circular Tour

/*
The structure of petrolPump is 
struct petrolPump
{
    int petrol;
    int distance;
};*/

/*You are required to complete this method*/
class Solution{
  public:
  
    //Function to find starting point where the truck can start to get through
    //the complete circle without exhausting its petrol in between.
    int tour(petrolPump p[],int n)
    {
       //Your code here
           int deficitpetrol=0;
       int balancepetrol=0;
       int start=0;
       
       for(int i=0;i<n;i++){
           balancepetrol+=p[i].petrol-p[i].distance;
           if(balancepetrol<0){
               deficitpetrol+=balancepetrol;
               start=i+1;
               balancepetrol=0;
           }
       }
       if(deficitpetrol+balancepetrol>=0){
           return start;
       }
       return -1;
    }
};