2073. Time Needed to Buy Tickets

There are n people in a line queuing to buy tickets, where the 0th person is at the front of the line and the (n - 1)th person is at the back of the line.

You are given a 0-indexed integer array tickets of length n where the number of tickets that the ith person would like to buy is tickets[i].

Each person takes exactly 1 second to buy a ticket. A person can only buy 1 ticket at a time and has to go back to the end of the line (which happens instantaneously) in order to buy more tickets. If a person does not have any tickets left to buy, the person will leave the line.

Return the time taken for the person at position k (0-indexed) to finish buying tickets.

 

Example 1:

Input: tickets = [2,3,2], k = 2
Output: 6
Explanation: 
- In the first pass, everyone in the line buys a ticket and the line becomes [1, 2, 1].
- In the second pass, everyone in the line buys a ticket and the line becomes [0, 1, 0].
The person at position 2 has successfully bought 2 tickets and it took 3 + 3 = 6 seconds.

Example 2:

Input: tickets = [5,1,1,1], k = 0
Output: 8
Explanation:
- In the first pass, everyone in the line buys a ticket and the line becomes [4, 0, 0, 0].
- In the next 4 passes, only the person in position 0 is buying tickets.
The person at position 0 has successfully bought 5 tickets and it took 4 + 1 + 1 + 1 + 1 = 8 seconds.

 

Constraints:

  • n == tickets.length
  • 1 <= n <= 100
  • 1 <= tickets[i] <= 100
  • 0 <= k < n

2073. Time Needed to Buy Tickets
struct Solution;

impl Solution {
    fn time_required_to_buy(tickets: Vec<i32>, k: i32) -> i32 {
        let mut res = 0;
        let n = tickets.len();
        let mut arr = vec![0; n];
        let mut i = 0;
        let k = k as usize;
        while arr[k] != tickets[k] {
            if arr[i] < tickets[i] {
                arr[i] += 1;
                res += 1;
            }

            i += 1;
            i %= n;
        }
        res
    }
}

#[test]
fn test() {
    let tickets = vec![2, 3, 2];
    let k = 2;
    let res = 6;
    assert_eq!(Solution::time_required_to_buy(tickets, k), res);
    let tickets = vec![5, 1, 1, 1];
    let k = 0;
    let res = 8;
    assert_eq!(Solution::time_required_to_buy(tickets, k), res);
}