2016秋季练习

来源：lightOJ1064

很水的DP

代码：#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
int n,x;
const int MAXN = 200;
const int N = 50;
LL dp
[MAXN];
LL a
;
inline LL gcd(LL a,LL b) {
if(!b) return a;
else return gcd(b,a%b);
}
inline void ini(){
a[0] = 1;
a[1] = 6;
for(int i=2;i<N;i++) a[i] = a[i-1]*6;
return ;
}
inline void DP(){
memset(dp,0,sizeof dp);
for(int i=1;i<=6;i++) dp[1][i] = 1;
for(int i=1;i<=26;i++) {
for(int j=1;j<=i*6;j++){
if(!dp[i][j]) continue;
for(int k=1;k<=6;k++){
dp[i+1][j+k] += dp[i][j];
}
}
}
}
int main(){
int T,nc = 1;
ini();
DP();
scanf("%d",&T);
while(T--){
scanf("%d%d",&n,&x);
LL sum = 0,ans = 0;
int maxn = n*6;
printf("Case %d: ",nc++);
if(x>maxn) {
puts("0");
continue;
}
for(int i=x;i<=maxn;i++) {
ans += dp
[i];
}
sum = a
;
if(sum == ans ){
puts("1");
continue;
}
LL tmp = gcd(ans,sum);
printf("%lld/%lld\n",ans/tmp,sum/tmp);
}

return 0;
}