07-图4. Saving James Bond - Hard Version (30)

本题测试点5是从小岛范围内可以直接跳到岸边……
测试点4是验证步数第一跳最小的情况，刚开始没有考虑回溯，所以错了……

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>using namespace std;const int inf=1<<30;struct node{    double x,y;} a[100+5];int n,vis[100+5],b[100+5],ans[100+5],cnt;double d,ansfirst,nowfirst;int dis(node d1,node d2){    if(d*d<(d1.x-d2.x)*(d1.x-d2.x)+(d1.y-d2.y)*(d1.y-d2.y)) return 0;    return 1;}int first(int d1){    if(sqrt(a[d1].x*a[d1].x+a[d1].y*a[d1].y)>d+7.5) return 0;    else return 1;}double first1(int d1){    return sqrt(a[d1].x*a[d1].x+a[d1].y*a[d1].y)-7.5;}int safe(node d1){    if(d1.x>=50-d) return 1;    if(d1.y>=50-d) return 1;    if(d1.x<=-50+d) return 1;    if(d1.y<=-50+d) return 1;    return 0;}void dfs(int d1,int now){    int i;    if(safe(a[d1]))    {        //printf("%d %.2f\n",now,nowfirst);        if(now<cnt)        {            for(i=0; i<now; i++)                ans[i]=b[i];            cnt=now;            ansfirst=nowfirst;        }        else if(now==cnt&&ansfirst>nowfirst)        {            for(i=0; i<now; i++)                ans[i]=b[i];            cnt=now;            ansfirst=nowfirst;        }        return ;    }    else    {        for(i=1; i<=n; i++)        {            if(!vis[i]&&dis(a[d1],a[i]))            {                vis[i]=1;                b[now]=i;                dfs(i,now+1);                vis[i]=0;            }        }    }    return;}int main(){    int i;    while(~scanf("%d%lf",&n,&d))    {        a[0].x=a[0].y=0;        for(i=1; i<=n; i++)        {            scanf("%lf%lf",&a[i].x,&a[i].y);        }        if(d+7.5>=50)        {            printf("1\n");            return 0;        }        ansfirst=(double)inf;        cnt=inf;        memset(ans,0,sizeof(ans));        for(i=1; i<=n; i++)        {            memset(vis,0,sizeof(vis));            if(!vis[i]&&first(i))            {                nowfirst=first1(i);                if(safe(a[i]))                {                    if(ansfirst>nowfirst)                    {                        ans[0]=i;                        cnt=1;                        ansfirst=nowfirst;                    }                }                vis[i]=1;                memset(b,0,sizeof(b));                b[0]=i;                dfs(i,1);            }        }        if(cnt==inf) printf("0\n");        else        {            printf("%d\n",cnt+1);            for(i=0; i<cnt; i++)            {                printf("%.0f %.0f\n",a[ans[i]].x,a[ans[i]].y);            }        }    }    return 0;}