求組合數

一、求 C(n,m)code 把n!與m階乘約分爲 (m+1)*(m+2)...n。io 以後除以(n-m)！class LL combination(int n, int m){ if(m < n-m) m = n-m; LL ans = 1; for(int i = m+1; i <= n; ++i) ans *= i; for(int i = 1; i <= n-m; ++i) an

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