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There are n boys and m girls attending a theatre club. To set a play "The Big Bang Theory", they need to choose a group containing exactly t actors containing no less than 4 boys and no less than one girl. How many ways are there to choose a group? Of course, the variants that only differ in the composition of the troupe are considered different.
Perform all calculations in the 64-bit type: long long for С/С++, int64 for Delphi and long for Java.
Input
The only line of the input data contains three integers n, m, t (4 ≤ n ≤ 30, 1 ≤ m ≤ 30, 5 ≤ t ≤ n + m).
Output
Find the required number of ways.
Please do not use the %lld specificator to read or write 64-bit integers in С++. It is preferred to use cin, cout streams or the %I64d specificator.
Sample Input
5 2 5
10
4 3 5
3
n个人，男生大于四个，女生大于一个，高中的排列组合
1 #include<iostream> 2 #include<cstdio> 3 #include<cmath> 4 typedef long long ll; 5 using namespace std; 6 ll fun(ll a, ll b) 7 { 8 ll temp=1; 9 for(int j=1;j<=b; j++) 10 { 11 temp=temp*a/j; 12 a--; 13 } 14 return temp; 15 } 16 int main() 17 { 18 ll m,n,t; 19 int i,j; 20 cin>>m>>n>>t; 21 ll sum=0; 22 for(i=4;i<t&&i<=m;i++) 23 { 24 if(t-i>=1&&t-i<=t-4&&t-i<=n) 25 sum=sum+fun(m,i)*fun(n,t-i); 26 } 27 cout<<sum<<endl; 28 return 0; 29 }
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原文地址：http://www.cnblogs.com/Aa1039510121/p/5693357.html
