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11050 : 이항계수 (Binomial Coefficient) [C++]

이항계수 문제를 풀기 전에 이항계수가 무엇인지부터 알아보자!

이항계수는 조합을 의미하며, 1보다 큰 정수 N과 0보다 크고 N보다 작은 정수 K로 이루어진다.

식은 nCk = n! / (k! * (n-k)!)이다.

이번 문제는 입력받는 값의 범위가 낮아 위의 식만 그대로 구현하면 되는 문제이다.

int Factorial(int n)
{
 if ((n == 1) || (n == 0))
  return 1;
 else
  return Factorial(n - 1) * n;
}

int main()
{
 int N;
 int K;

 cin >> N >> K;
    
    if(1 <= N && N <= 10 && 0 <= K && K <= N)
     cout << Factorial(N) / (Factorial(K) * Factorial(N - K));

 return 0;
}
<소스 코드>

*Source of the problem = https://www.acmicpc.net/problem/11050
*문제 출처 : BAEKJOON ONLINE JUDGE

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