%%%%http://blog.csdn.net/popoqqq/article/details/43926365
1 #include<bits/stdc++.h> 2 #define INF 0x7fffffff 3 #define LL long long 4 #define N 100005 5 using namespace std; 6 inline int ra() 7 { 8 int x=0,f=1; char ch=getchar(); 9 while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();} 10 while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();} 11 return x*f; 12 } 13 double p,ans,a[101],f[101][101],g[101][101]; 14 int main() 15 { 16 int n=ra(),m=ra(); 17 for (int i=1; i<=n; i++) 18 scanf("%lf",&a[i]); 19 int st=ra(); 20 scanf("%lf",&p); 21 memset(f,0xc2,sizeof(f)); 22 for (int i=1; i<=n; i++) 23 f[i][i]=0; 24 for (int i=1; i<=m; i++) 25 { 26 int x=ra(),y=ra(); 27 f[x][y]=a[y]; 28 } 29 double tmp=p; 30 for (int T=0; T<=70; T++,tmp*=tmp) 31 { 32 memset(g,0xc2,sizeof(g)); 33 for (int k=1; k<=n; k++) 34 for (int i=1; i<=n; i++) 35 for (int j=1; j<=n; j++) 36 g[i][j]=max(g[i][j],f[i][k]+f[k][j]*tmp); 37 memcpy(f,g,sizeof(f)); 38 } 39 for (int i=1; i<=n; i++) 40 ans=max(ans,f[st][i]); 41 printf("%.1lf ",ans*p+a[st]); 42 return 0; 43 }