BZOJ3275【最小割】

要先判断a*a+b*b==c*c这个条件.再判断gcd(a,b)==1.不然会TLE.

/* I will wait for you */ #include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<ctime>#include<algorithm>#include<iostream>#include<fstream>#include<vector>#include<queue>#include<deque>#include<set>#include<map>#include<string>#define make(a,b) make_pair(a,b)#define fi first#define se second using namespace std; typedef long long LL;typedef unsigned long long ULL;typedef pair<int,int> PII; const int maxn=6010;const int maxm=1000010;const int maxs=26;const int INF=1<<29;const int P=1000000007;const double error=1e-9; struct edge{ int v,a,next; }e[maxm]; int s,t,ans,cnt,head[maxn],dis[maxn],cur[maxn],q[maxn],c[maxn]; int gcd(int a,int b){    return a?gcd(b%a,a):b;} int allow(int a,int b){    int c=sqrt(a*a+b*b);    return c*c==(a*a+b*b)&&gcd(a,b)==1;} void insert(int u,int v,int a){    e[cnt]=(edge){v,a,head[u]},head[u]=cnt++;    e[cnt]=(edge){u,0,head[v]},head[v]=cnt++;} int bfs(){    memset(dis,-1,sizeof(dis));    int he=0,ta=1;q[0]=s,dis[s]=0;         while(he!=ta)    {        int u=q[he++];        for(int i=head[u],v;i!=-1;i=e[i].next)            if(e[i].a&&dis[v=e[i].v]==-1) dis[v]=dis[u]+1,q[ta++]=v;    }    return dis[t]!=-1;} int dfs(int u,int a){    if(u==t) return a;    int f,flow=0;    for(int i=cur[u],v;a&&i!=-1;i=e[i].next)    {        if(e[i].a&&dis[v=e[i].v]==dis[u]+1&&(f=dfs(v,min(a,e[i].a)))>0)        {            e[i].a-=f,e[i^1].a+=f,a-=f,flow+=f;            if(e[i].a) cur[u]=i;        }    }    if(!flow) dis[u]=-1;    return flow;} void dinic(){    while(bfs()) memcpy(cur,head,sizeof(cur)),ans-=dfs(s,INF);}     int main(){    int n;scanf("%d",&n);    s=2*n+1,t=2*n+2;     memset(head,-1,sizeof(head));         for(int i=1;i<=n;i++)    {        scanf("%d",&c[i]);ans+=2*c[i];        insert(s,i,c[i]),insert(n+i,t,c[i]);    }    for(int i=1;i<=n;i++) for(int j=1;j<=n;j++)        if(allow(c[i],c[j])) insert(i,n+j,INF),insert(j,n+i,INF);         dinic();printf("%d\n",ans/2);         return 0;}