54 lines
1.1 KiB
C++
54 lines
1.1 KiB
C++
#include <stdio.h>
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#include <iostream>
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#include <map>
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#include <stack>
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#include <vector>
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#include <math.h>
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#include <string.h>
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#include <queue>
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#include <string>
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#include <stdlib.h>
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#include <algorithm>
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#define LL long long
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#define _LL __int64
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#define eps 1e-8
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#define PI acos(-1.0)
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using namespace std;
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int n,m;
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int vis[210];
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int a[210];
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int sum,cnt;
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double p,q;
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int main()
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{
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while(~scanf("%d",&n))
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{
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sum = 0;
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cnt = 0;
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memset(vis,0,sizeof(vis));
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for(int i = 1; i <= n; i++)
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{
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cin >> a[i];
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sum += a[i];
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}
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p = (sum*1.0)/n;
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scanf("%d",&m);
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int x;
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for(int i = 1; i <= m; i++)
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{
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cin >> x;
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if(vis[x]) continue;
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cnt++;
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vis[x] = 1;
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}
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q = (cnt*1.0)/n;
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if(fabs(p) < eps)
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cout << "0.00" << endl;
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else if(fabs(q-1) < eps)
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cout << "inf" << endl;
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else
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printf("%.2lf\n",p/(1-q));
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}
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return 0;
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}
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