1688. Count of Matches in Tournament
Description
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, andn / 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
Solution 1: Quick Thinking
From the problem description, we know that there are $n$ teams in total. Each pairing will eliminate one team. Therefore, the number of pairings is equal to the number of teams eliminated, which is $n  1$.
The time complexity is $O(1)$, and the space complexity is $O(1)$.
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