Average Waiting time (Simulation based question)

Problem link

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Approach

1. Initially, when the chef is not doing anything and a customer arrives, the waiting time for the customer to get a particular dish ordered is nothing but just the preparation time.

2. Now, let's suppose the chef is preparing the food and meanwhile another customer arrives. In that case, the waiting time would be the last preparation time plus the new preparation time minus the time when the customer arrived.

3. Another possible case is that the chef has prepared and delivered the dish and is now not doing anything. In that case, we need to deal with this customer as we did in step 1.

4. We will add up the waiting time and divide by the number of customers which is give by customers.size();.

Code

class Solution {
public:
    double averageWaitingTime(vector<vector<int>>& customers) {
        int n = customers.size();
        double prep = customers[0][0]+customers[0][1];
        double w = prep - customers[0][0]; 
        for(int i = 1;i<n;i++){
            if(prep>customers[i][0]){
            prep = prep + customers[i][1];
            w = w + (prep - customers[i][0]);
            }
            else{
                prep = customers[i][0]+customers[i][1];
                w = w + (prep - customers[i][0]); 
            }
        }
        return w/n;
    }
};

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Ujjwal Sharma