40 lines
1.1 KiB
C++
40 lines
1.1 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<algorithm>
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#include<cmath>
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#include<vector>
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using namespace std;
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int n, a[12];
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double dp[1<<12];
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double cal(int a, int b, int c){
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if(a+b<=c) return 0.0;
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double p = (a+b+c)*0.5;
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return sqrt(p*(p-a)*(p-b)*(p-c));
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}
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vector<int> V;
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int main(){
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while(~scanf("%d", &n) && n){
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memset(dp, 0, sizeof(dp));
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for(int i=0; i<n; i++) scanf("%d", a+i);
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sort(a, a+n);
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V.clear();
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for(int i=0; i<n; i++){
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for(int j=i+1; j<n; j++){
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for(int k=j+1; k<n; k++){
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int st = (1<<i)|(1<<j)|(1<<k);
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dp[st] = cal(a[i], a[j], a[k]);
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if(a[i]+a[j]>a[k]) V.push_back(st);
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}
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}
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}
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for(int i=0; i<(1<<n); i++){
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for(int j=0; j<V.size(); j++){
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if(i&V[j]) continue;
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dp[i|V[j]] = max(dp[i|V[j]], dp[i]+dp[V[j]]);
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}
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}
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printf("%.2f\n", dp[(1<<n)-1]);
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}
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return 0;
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}
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