59 lines
1.1 KiB
C++
59 lines
1.1 KiB
C++
#include<iostream>
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#include<cstdio>
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#include<algorithm>
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using namespace std ;
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#define M 100000 + 10
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#define eps 1e-4
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int A[M] ;
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int n ;
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int m ;
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int slove(double x)
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{
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int sum = 0 ;
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double d = A[0] ;
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d += 2 * x ;
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int i = 0 ;
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++ sum ;
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while(d < A[m -1] * 1.0 )
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{
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while(A[i] <= d) ++ i ;
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d = A[i] + 2 * x ;
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sum ++ ;
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}
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return sum ;
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}
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double Find(double left , double right)
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{
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double mid ;
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while(right - left > eps)
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{
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mid = left + (right - left) / 2 ;
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if(slove(mid) <= n)
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right = mid ;
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else left = mid +eps ;
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}
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return left ;
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}
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int main()
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{
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int cas ;
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double low ;
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double high ;
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double ans ;
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while(scanf("%d",&cas) != EOF)
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{
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while(cas --)
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{
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scanf("%d%d",&n,&m) ;
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for(int i = 0 ;i < m ; ++ i)
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scanf("%d",&A[i]) ;
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sort(A , A+ m) ;
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low = 0 ;
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high = A[m -1] * 1.0 / n ;
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ans = Find(low , high) ;
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printf("%.1lf\n",ans) ;
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}
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}
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return 0 ;
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}
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