Average Waiting Time

summary

• Calculate the average waiting time of customers in a restaurant.

approach

• This solution uses a greedy approach to calculate the average waiting time of customers
• It iterates over the customers and calculates the waiting time for each customer based on the time the chef is idle
• The total waiting time is then divided by the number of customers to get the average waiting time.

complexity

• O(n)

explain

• The solution works by iterating over the customers and calculating the waiting time for each customer
• If the customer arrives after the chef is idle, the waiting time is the time the chef has been idle plus the preparation time
• If the customer arrives before the chef is idle, the waiting time is the time the chef has been idle plus the preparation time minus the time the customer arrived
• The total waiting time is then divided by the number of customers to get the average waiting time.

Solution Code:

class Solution {
public:
    double averageWaitingTime(vector>& customers) {
        long long totalWait = 0;
        long long time = 0;
        for(int i = 0 ; i < customers.size(); i++){
            int arrival = customers[i][0];
            int prepareTime = customers[i][1];

            if (arrival > time){
                time = arrival + prepareTime;
                totalWait += prepareTime;
            } else {
                totalWait += time - arrival + prepareTime;
                time += prepareTime;
            }
        }
        return (double)totalWait / customers.size();
    }
};