9.5中兴笔试编程2代码
使用BigInteger实现
做法十分暴力，一定要超时的，不知道用例有没有作时间限制。
贴出来给大家图一乐⑧
import java.math.BigInteger;
import java.util.Scanner;
public class Solution2 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n =sc.nextInt();
int m =sc.nextInt();
int k =sc.nextInt();
BigInteger sum=new BigInteger("0");
for (int i = 3; i <= n; i++) {
for (int j = 2; j <= m; j++) {
if(i+j==k) {
BigInteger temp1 = get(new BigInteger(n+"")).divide(get(new BigInteger(i+"")).multiply(get(new BigInteger((n-i)+""))));
BigInteger temp2 = get(new BigInteger(m+"")).divide(get(new BigInteger(j+"")).multiply(get(new BigInteger((m-j)+""))));
sum= sum.add((temp1.multiply(temp2)));
if (sum.intValue() > 1000000007) {
sum = sum.remainder(new BigInteger("1000000007"));
}
}
}
}
System.out.println(sum.remainder(new BigInteger("1000000007")));
}
private static BigInteger get(BigInteger m) {
BigInteger temp = new BigInteger("1");
if (m.intValue()==0) {
return temp;
}
for (int i = 1; i <= m.intValue(); i++) {
temp = temp.multiply(new BigInteger(i+""));
}
return temp;
}
} 
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