codeforce 580D Kefa and Dishes （状压DP）

/* http://codeforces.com/contest/580/problem/D */

#include<bits/stdc++.h>

#define clr(x,y) memset((x),(y),sizeof(x))

using namespace std;
typedef long long LL;

const int maxn=1<<18;

LL dp[maxn+5][20];
LL A[20];
LL B[20][20];

int Count(int x)
{
int res=0;
while (x>0)
{
x-=x&(-x);
++res;
}
return res;
}

int n,m,k;

int main(void)
{
#ifdef ex
freopen ("../in.txt","r",stdin);
//freopen ("../out.txt","w",stdout);
#endif

int p,q;
LL t;

scanf("%d%d%d",&n,&m,&k);
for (int i=0;i<=n-1;++i)
{
scanf("%I64d",&A[i]);
}
for (int i=1;i<=k;++i)
{
scanf("%d%d%I64d",&p,&q,&t);
B[p-1][q-1]=t;
}

LL ans=0;
clr(dp,0);
for (int i=0;i<=n-1;++i)
{
dp[1<<i][i]=A[i];
}
int s=(1<<n)-1;
for (int mask=0;mask<=s;++mask)
{
for (int i=0;i<=n-1;++i)
{
if (mask>>i & 1)
{
for (int j=0;j<=n-1;++j)
{
if (!(mask>>j & 1))
{
dp[mask|1<<j][j]=max(dp[mask|1<<j][j],dp[mask][i]+B[j][i]+A[j]);
}
}
}
}
}

for (int mask=0;mask<=s;++mask) /*处理完了之后再更新答案，可以避免遗漏*/
{
if (Count(mask)==m)
for (int i=0;i<=n-1;++i)
{
ans=max(ans,dp[mask][i]);
}
}
printf("%I64d\n",ans);
}