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https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
31 lines
655 B
C++
31 lines
655 B
C++
#include <iostream>
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#include <cstdio>
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#include <cstring>
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#include <algorithm>
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using namespace std;
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int n;
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double f[1<<20], p[25];
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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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for(int i=0; i<n; i++)
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scanf("%lf", &p[i]);
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int all=(1<<n)-1;
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f[all]=0;
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for(int s=all-1; s>=0; s--)
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{
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double temp=0;
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f[s]=1;
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for(int i=0; i<n; i++)
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{
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if(s&(1<<i)) continue;
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f[s]+=f[s|(1<<i)]*p[i];
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temp+=p[i];
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}
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f[s]/=temp;
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}
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printf("%lf\n", f[0]);
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}
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}
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