Formatted question description: https://leetcode.ca/all/1688.html

# 1688. Count of Matches in Tournament (Easy)

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

Related Topics:
Backtracking

## Solution 1.

// OJ: https://leetcode.com/problems/count-of-matches-in-tournament/

// Time: O(logN)
// Space: O(1)
class Solution {
public:
int numberOfMatches(int n) {
int ans = 0;
for (; n > 1; n = n / 2 + n % 2) ans += n / 2;
return ans;
}
};


## Solution 2.

Each match removes a loser. To get one winner from the n teams, we need n - 1 matches.

// OJ: https://leetcode.com/problems/count-of-matches-in-tournament/

// Time: O(1)
// Space: O(1)
class Solution {
public:
int numberOfMatches(int n) {
return n - 1;
}
};


Java

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