排列組合
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 3419 Accepted Submission(s): 1429
#include"iostream"
#include"cstdio"
#include"cstring"
using namespace std;
const int maxn = 10;
double c1[maxn + 1], c2[maxn + 2];
double fac[maxn + 1];
int num[maxn + 1];
void MakeFac(){
fac[0] = 1.0;
for(int i = 1;i <= maxn;i ++)
fac[i] = fac[i - 1] * i;
}
int min(int x, int y){
return x < y ? x : y;
}
int main(){
int n, m, t;
MakeFac();
while(scanf("%d%d", &n, &m) != EOF){
memset(c1, 0, sizeof c1);
memset(c2, 0, sizeof c2);
for(int i = 1;i <= n;i ++){
scanf("%d",&t);
num[i] = min(t, m);
}
for(int j = 0;j <= num[1];j ++)
c1[j] = 1.0/fac[j];
for(int i = 2;i <= n;i ++){
if(num[i] == 0) continue;
for(int j = 0;j <= m;j ++)
for(int k = 0;k <= num[i] && k + j <= m;k ++)
c2[k + j] += c1[j] / fac[k];
for(int j = 0;j <= m;j ++){
c1[j] = c2[j];
c2[j] = 0;
}
}
printf("%.0lf\n",c1[m]*fac[m]);
}
return 0;
}