Time Needed To Buy Tickets

Problem Summary

There are n people standing in a queue to buy tickets. The i-th person wants to buy tickets[i] tickets. Each person buys one ticket per turn, then goes to the back of the queue (if they still need more). Find the total time for the person at position k (0-indexed) to finish buying all their tickets.

Constraints:

The queue has between 1 and 100 people.
Each person wants between 1 and 100 tickets.
k is a valid index between 0 and n - 1.

Techniques

Array
Queue
Simulation

Solution

function timeRequiredToBuy(tickets: number[], k: number): number {
    let numberOfTicketsNeeded = tickets[k]
    let time = 0

    while (tickets[k] > 0) {
        tickets[0]--
        let outOfQueue = tickets.shift()!

        if (outOfQueue > 0) {
            tickets.push(outOfQueue)
        }

        time++

        if (k === 0 && outOfQueue === 0) {
            return time
        }

        k = k > 0 ? --k % tickets.length : tickets.length - 1
    }

    return time
};