HDU 2013 ACM/ICPC Asia Regional Hangzhou Online ------ Zhuge Liang's Mines

http://acm.hdu.edu.cn/showproblem.php?pid=4739

这题是dfs，只需一个一个搜就可以了

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
struct node
{
    int x,y;
}s[50];
int N,ans,v[50];
int cmp(const void *a,const void *b)
{
    struct node *c=(struct node *)a;
    struct node *d=(struct node *)b;
    if(c->y==d->y)
        return c->x>d->x;
    else return c->y>d->y;
}
void dfs(int num,int sum)/*num记录点的位置，sum记录总共可以移动的地雷数量*/
{
    int i,j,cut,n1,n2;
    if(ans<sum)ans=sum;
    for(i=num;i<N;i++)
    {
        if(v[i])continue;
        v[i]=1;
        for(j=i+1;j<N;j++)
        {
            if(v[j]||s[i].x!=s[j].x||s[i].y==s[j].y)
                continue;
            v[j]=1;
            cut=abs(s[j].y-s[i].y);
            for (n1=0;n1<N;n1++)
                if (s[n1].x==s[i].x+cut && s[n1].y==s[i].y && !v[n1]) break;//找到对应的那个是否存在
            if (n1==N)
            {
                v[j]=0;
                continue;
            }
            v[n1]=1;
            for (n2=0;n2<N;n2++)
                if (s[n2].x==s[j].x+cut && s[n2].y==s[j].y && !v[n2]) break;
            if (n2==N)
            {
                v[j]=v[n1]=0;
                continue;
            }
                v[n2]=1;
                dfs(i+1,sum+4);
                v[j]=v[n1]=v[n2]=0;
        }
        v[i]=0;
    }
}
int main()
{
    int i,j;
    struct node temp;
    while(scanf("%d",&N),N!=-1)
    {
        for(i=0;i<N;i++)
            v[i]=0;
        for(i=0;i<N;i++)
            scanf("%d%d",&s[i].x,&s[i].y);
        /*qsort(s,N,sizeof(s[0]),cmp);*/
        /*for(i=0;i<N-1;i++)
        {
            for(j=i;j<N-1;j++)
                if(s[j].y>s[j+1].y)
                temp=s[j],s[j]=s[j+1],s[j+1]=temp;
                else if(s[j].y==s[j+1].y&&s[j].x>s[j+1].x)
                temp=s[j],s[j]=s[j+1],s[j+1]=temp;
        }*/
        /*for(i=0;i<N;i++)
            printf("(%d,%d)
",s[i].x,s[i].y);*/
        ans=0;
        dfs(0,0);
        printf("%d
",ans);
    }
    return 0;
}