57 lines
1.2 KiB
C++
57 lines
1.2 KiB
C++
#include <iostream>
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#include <cstdio>
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#include <cstring>
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#include <queue>
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using namespace std;
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struct p
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{
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int a[50][2];
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}p[50010];
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double b[51000];
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queue<int> q;
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int s,t,n;
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double m;
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int main()
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{
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while(scanf("%d",&n)!=EOF)
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{
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memset(p,-1,sizeof(p));
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for(int i=0;i<51000;i++)
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b[i]=-1;
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for(int i=1;i<=n;i++)
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{
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int x;
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scanf("%d",&x);
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for(int j=0;j<x;j++)
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{
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scanf("%d",&p[i].a[j][0]);
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scanf("%d",&p[i].a[j][1]);
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}
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}
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scanf("%d%d%lf",&s,&t,&m);
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b[s]=0;
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q.push(s);
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int hd;
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while(!q.empty())
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{
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hd=q.front();
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q.pop();
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for(int i=0;i<50;i++)
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{
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if(p[hd].a[i][0]==hd)
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continue;
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if(p[hd].a[i][0]!=-1&&(b[p[hd].a[i][0]]+1<1e-8||b[p[hd].a[i][0]]>b[hd]+(100.0-b[hd])*p[hd].a[i][1]/100))
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{
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q.push(p[hd].a[i][0]);
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b[p[hd].a[i][0]]=b[hd]+(100.0-b[hd])*p[hd].a[i][1]/100;
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}
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}
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}
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if(b[t]+1<1e-8)
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cout<<"IMPOSSIBLE!\n";
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else
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printf("%.2lf\n",m*b[t]/100);
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}
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return 0;
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}
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