HDU5135Little Zu Chongzhi's Triangles(状态压缩DP)

#include<bits/stdc++.h>
using namespace std;
int s[12];
double dp[1<<12];
vector<int> v;
double cul(int a, int b, int c)
{
if(a + b <= c)
return 0.0;
double p = (a + b + c) * 0.5;
return sqrt(p*(p-a)*(p-b)*(p-c));
}
int main()
{
int n;
while(scanf("%d", &n) != EOF && n)
{
v.clear();
memset(dp, 0, sizeof(dp));
for(int i = 0; i < n; i++)
scanf("%d", &s[i]);
sort(s, s+n);
for(int i = 0; i < n; i++)
for(int j = i+1; j < n; j++)
for(int k = j+1; k < n; k++)
{
int st = (1<<i) | (1<<j) | (1<<k);
dp[st] = cul(s[i], s[j], s[k]);
if(s[i] + s[j] > s[k])
v.push_back(st);
}
for(int i = 0; i < (1 << n); i++)
for(int j = 0; j < v.size(); j++)
{
if(i & v[j])
continue;
dp[i|v[j]] = max(dp[i|v[j]], dp[i] + dp[v[j]]);
}
printf("%.2f\n", dp[(1<<n)-1]);
}
return 0;
}