bzoj3275: Number(最小割)

3275: Number

题目：传送门

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题解：

　　 双倍经验@bzoj3158

　　

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代码：

 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<cmath>
 #include<algorithm>
 #define qread(x) x=read()
 using namespace std;
 const int inf=;
 int n,st,ed,sum;
 int A[],B[];
 struct node
 {
     int x,y,c,next,other;
 }a[];int len,last[];
 void ins(int x,int y,int c)
 {
     int k1,k2;
     k1=++len;
     a[len].x=x;a[len].y=y;a[len].c=c;
     a[len].next=last[x];last[x]=len;

     k2=++len;
     a[len].x=y;a[len].y=x;a[len].c=;
     a[len].next=last[y];last[y]=len;

     a[k1].other=k2;
     a[k2].other=k1;
 }
 int list[],h[],head,tail;
 bool bt_h()
 {
     memset(h,,sizeof(h));h[st]=;
     list[]=st;head=;tail=;
     while(head!=tail)
     {
         int x=list[head];
         for(int k=last[x];k;k=a[k].next)
         {
             int y=a[k].y;
             if(h[y]== && a[k].c>)
             {
                 h[y]=h[x]+;
                 list[tail++]=y;
             }
         }
         head++;
     }
     if(h[ed]>)return true;
     return false;
 }
 int find_flow(int x,int flow)
 {
     if(x==ed)return flow;
     int s=,t;
     for(int k=last[x];k;k=a[k].next)
     {
         int y=a[k].y;
         if(h[y]==h[x]+ && a[k].c> && flow>s)
         {
             s+=t=find_flow(y,min(a[k].c,flow-s));
             a[k].c-=t;a[a[k].other].c+=t;
         }
     }
     if(s==)h[x]=;
     return s;
 }
 int gcd(int x,int y) {if(x>y)swap(x,y);if(x==)return y;return gcd(y%x,x);}
 bool pd(int x,int y)
 {
     int t=int(sqrt(double(x*x+y*y)));
     if(t*t!=x*x+y*y)return true;
     if(gcd(x,y)>)return true;
     return false;
 }
 int main()
 {
     freopen("number.in","r",stdin);
     freopen("number.out","w",stdout);
     sum=;
     scanf("%d",&n);
     len=;memset(last,,sizeof(last));
     for(int i=;i<=n;i++){scanf("%d",&B[i]);sum+=B[i];}
     st=n+;ed=st+;
     for(int i=;i<=n;i++)
     {
         if(B[i]%==)ins(st,i,B[i]);
         else ins(i,ed,B[i]);
     }
     for(int i=;i<=n;i++)
         for(int j=;j<=n;j++)if(i!=j)
             if((B[i]%==) && (B[j]%==) && pd(B[i],B[j])==false)
                 ins(i,j,);
     int ans=;
     while(bt_h())ans+=find_flow(st,);
     printf("%d\n",sum-ans);
     return ;
 }