1688. Count of Matches in Tournament

You are given an integer n, the number of teams in a tournament that has strange rules:

  • If the current number of teams is even, each team gets paired with another team. A total of n / 2 matches are played, and n / 2 teams advance to the next round.
  • If the current number of teams is odd, one team randomly advances in the tournament, and the rest gets paired. A total of (n - 1) / 2 matches are played, and (n - 1) / 2 + 1 teams advance to the next round.

Return the number of matches played in the tournament until a winner is decided.

 

Example 1:

Input: n = 7
Output: 6
Explanation: Details of the tournament: 
- 1st Round: Teams = 7, Matches = 3, and 4 teams advance.
- 2nd Round: Teams = 4, Matches = 2, and 2 teams advance.
- 3rd Round: Teams = 2, Matches = 1, and 1 team is declared the winner.
Total number of matches = 3 + 2 + 1 = 6.

Example 2:

Input: n = 14
Output: 13
Explanation: Details of the tournament:
- 1st Round: Teams = 14, Matches = 7, and 7 teams advance.
- 2nd Round: Teams = 7, Matches = 3, and 4 teams advance.
- 3rd Round: Teams = 4, Matches = 2, and 2 teams advance.
- 4th Round: Teams = 2, Matches = 1, and 1 team is declared the winner.
Total number of matches = 7 + 3 + 2 + 1 = 13.

 

Constraints:

  • 1 <= n <= 200

Rust Solution

struct Solution;

impl Solution {
    fn number_of_matches(mut n: i32) -> i32 {
        let mut res = 0;
        while n > 1 {
            if n % 2 == 1 {
                res += 1;
            }
            n /= 2;
            res += n;
        }
        res
    }
}

#[test]
fn test() {
    let n = 7;
    let res = 6;
    assert_eq!(Solution::number_of_matches(n), res);
    let n = 14;
    let res = 13;
    assert_eq!(Solution::number_of_matches(n), res);
}

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