loj 1154(最大流+枚举汇点)

题目链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=26868

思路：拆点，容量为最多能跳的步数，然后设立一个超级源点，源点与各点两连边，容量为一开始的企鹅数，最后就是枚举汇点了，跑最大流验证即可。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<cmath>
using namespace std;
#define MAXN 222
#define MAXM 222222
#define inf 1<<30
#define FILL(a,b) memset(a,b,sizeof(a))

struct Edge{
    int v,cap,next;
}edge[MAXM];

int n,vs,vt,NV,NE,head[MAXN];
double d;


void Insert(int u,int v,int cap)
{
    edge[NE].v=v;
    edge[NE].cap=cap;
    edge[NE].next=head[u];
    head[u]=NE++;

    edge[NE].v=u;
    edge[NE].cap=0;
    edge[NE].next=head[v];
    head[v]=NE++;
}

int level[MAXN],gap[MAXN];
void bfs(int vt)
{
    FILL(level,-1);
    FILL(gap,0);
    queue<int>que;
    que.push(vt);
    level[vt]=0;
    gap[0]++;
    while(!que.empty()){
        int u=que.front();
        que.pop();
        for(int i=head[u];i!=-1;i=edge[i].next){
            int v=edge[i].v;
            if(level[v]!=-1)continue;
            level[v]=level[u]+1;
            gap[level[v]]++;
            que.push(v);
        }
    }
}

int pre[MAXN],cur[MAXN];
int SAP(int vs,int vt)
{
    bfs(vt);
    memcpy(cur,head,sizeof(head));
    int u=pre[vs]=vs,aug=inf,maxflow=0;
    gap[0]=NV;
    while(level[vs]<NV){
        bool flag=false;
        for(int &i=cur[u];i!=-1;i=edge[i].next){
            int v=edge[i].v;
            if(edge[i].cap>0&&level[u]==level[v]+1){
                flag=true;
                aug=min(aug,edge[i].cap);
                pre[v]=u;
                u=v;
                if(v==vt){
                    maxflow+=aug;
                    for(u=pre[u];v!=vs;v=u,u=pre[u]){
                        edge[cur[u]].cap-=aug;
                        edge[cur[u]^1].cap+=aug;
                    }
                    aug=inf;
                }
                break;
            }
        }
        if(flag)continue;
        int minlevel=NV;
        for(int i=head[u];i!=-1;i=edge[i].next){
            int v=edge[i].v;
            if(edge[i].cap>0&&level[v]<minlevel){
                cur[u]=i;
                minlevel=level[v];
            }
        }
        if(--gap[level[u]]==0)break;
        level[u]=minlevel+1;
        gap[level[u]]++;
        u=pre[u];
    }
    return maxflow;
}

struct Node{
    double x,y;
    int num,step;
}node[MAXN];

double Get_Dist(int i,int j)
{
    double d1=(node[i].x-node[j].x)*(node[i].x-node[j].x);
    double d2=(node[i].y-node[j].y)*(node[i].y-node[j].y);
    return sqrt(d1+d2);
}

void Build(int ed)
{
    NE=0;
    FILL(head,-1);
    vs=0,vt=2*n+1;
    NV=vt+1;
    for(int i=1;i<=n;i++){
        Insert(i,i+n,node[i].step);
        Insert(vs,i,node[i].num);
    }
    for(int i=1;i<=n;i++){
        for(int j=i+1;j<=n;j++){
            if(Get_Dist(i,j)<=d){
                Insert(i+n,j,inf);
                Insert(j+n,i,inf);
            }
        }
    }
    Insert(ed,vt,inf);
}

int main()
{
    int _case,ans,sum,flag,t=1;
    scanf("%d",&_case);
    while(_case--){
        scanf("%d%lf",&n,&d);
        sum=0;
        for(int i=1;i<=n;i++){
            scanf("%lf%lf%d%d",&node[i].x,&node[i].y,&node[i].num,&node[i].step);
            sum+=node[i].num;
        }
        flag=0;
        printf("Case %d:",t++);
        //枚举集中点
        for(int i=1;i<=n;i++){
            Build(i);
            if(SAP(vs,vt)==sum)flag=1,printf(" %d",i-1);
        }
        if(!flag)printf(" -1");
        puts("");
    }
    return 0;
}