[dfs]zoj 3761

大致思路：

       每一行的点和每一列的点都连上边，然后用dfs的方法把图变为一颗搜索树，然后由叶子向根删除节点即可

 

#include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
using namespace std;
const int nMax = 2010;
const int mMax = 3000008;
class edge{
public:
    int v,nex;
};edge e[mMax];
int k,head[nMax];
void addedge(int a,int b){
    e[k].v=b;
    e[k].nex=head[a];
    head[a]=k;k++;
}
class pxx{
public:
    int x,y;
}pos[nMax];
int n,m,vis[nMax],ope[nMax][3],cnt;

void dfs(int loc){
    vis[loc]=1;
    for(int i=head[loc];i;i=e[i].nex){
        int v=e[i].v;
        if(vis[v])continue;
        dfs(v);
        if(pos[v].x==pos[loc].x){
            if(pos[v].y>pos[loc].y){
                ope[cnt][0]=1;
                ope[cnt][1]=v;
                cnt++;
            }else{
                ope[cnt][0]=2;
                ope[cnt][1]=v;
                cnt++;
            }
        }else{
            if(pos[v].x>pos[loc].x){
                ope[cnt][0]=3;
                ope[cnt][1]=v;
                cnt++;
            }else{
                ope[cnt][0]=4;
                ope[cnt][1]=v;
                cnt++;
            }
        }
    }
}
int main(){
    int i,j;
    while(scanf("%d",&n)!=EOF){
        for(i=1;i<=n;i++){
            scanf("%d%d",&pos[i].x,&pos[i].y);
        }
        k=1;
        memset(head,0,sizeof(head));
        for(i=1;i<=n;i++){
            for(j=i+1;j<=n;j++){
                if(pos[i].x==pos[j].x||pos[i].y==pos[j].y){
                    addedge(i,j);
                    addedge(j,i);
                }
            }
        }
        int res=0;
        cnt=0;
        memset(vis,0,sizeof(vis));
        for(i=1;i<=n;i++){
            if(vis[i])continue;
            res++;
            dfs(i);
        }
        printf("%d\n",res);
        for(i=0;i<cnt;i++){
            printf("(%d, %d) ",pos[ope[i][1]].x,pos[ope[i][1]].y);
            if(ope[i][0]==1)printf("DOWN\n");
            else if(ope[i][0]==2)printf("UP\n");
            else if(ope[i][0]==3)printf("LEFT\n");
            else if(ope[i][0]==4)printf("RIGHT\n");
        }
    }
    return 0;
}