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

Solutions

class Solution {
public:
    int numberOfMatches(int n) {
        int res = 0;
        while (n > 1) {
            res += n / 2 + (n & 1);
            n >>= 1;
        }
        return res;
    }
};