A C

Problem Description Are you excited when you see the title "AC" ? If the answer is YES , AC it ; You must learn these two combination formulas in the school . If you have forgotten it , see the picture. Now I will give you n and m , and your task is to calculate the answer .   Input In the first line , there is a integer T indicates the number of test cases. Then T cases follows in the T lines. Each case contains a character 'A' or 'C', two integers represent n and m. (1<=n,m<=10)   Output For each case , if the character is 'A' , calculate A(m,n),and if the character is 'C' , calculate C(m,n). And print the answer in a single line.   Sample Input 2 A 10 10 C 4 2   Sample Output 3628800 6

题意：照公式计算。

for循环，n-m到n。

#include<stdio.h> #include<string.h> int main() { int m,n,t,i; char c; __int64 sum; scanf("%d",&t); while(t--) { scanf("%c",&c); if(c!='A'&&c!='C') { t++; continue; } scanf("%d%d",&n,&m); sum=1; if(c=='A') { for(i=n-m+1; i<=n; i++) { sum*=i; } } else if(c=='C') { for(i=n-m+1; i<=n; i++) { sum*=i; } for(i=1;i<=m;i++) { sum/=i; } } printf("%I64d\n",sum); } return 0; }