HDU 1245 Saving James Bond

HDU_1245

This topic first needs to traverse all vertices, add the points that can be reached for the first time to the SPFA queue, and set the values of d [] and step, the other d [I] And step [I] are initialized to INF. Then, the shortest and the shortest steps of each point are obtained, and all points are scanned, perform further processing on the points that can jump out of the lake.

#include<stdio.h>
#include<string.h>
#include<math.h>
double d[110],D,x[110],y[110];
int step[110],q[110],inq[110],reach[110];
double dis(int i,int j)
{
return sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
}
int main()
{
int i,j,k,n,N,u,v,ans_s,front,rear;
double temp,ans_d;
while(scanf("%d%lf",&n,&D)==2)
    {
        N=0;
for(i=0;i<n;i++)
        {
            scanf("%lf%lf",&x[N],&y[N]);
if(x[N]<50.0&&x[N]>-50.0&&y[N]<50.0&&y[N]>-50.0
            &&sqrt(x[N]*x[N]+y[N]*y[N])>7.5-1e-7)
                N++;
        }
if(D+1e-7>42.5)
        {
            printf("42.50 1\n");
continue;
        }
        front=rear=0;
        memset(inq,0,sizeof(inq));
for(i=0;i<N;i++)
        {
            temp=sqrt(x[i]*x[i]+y[i]*y[i])-7.5;
if(temp<D+1e-7)
            {
                d[i]=temp;
                step[i]=1;
                q[rear++]=i;
                inq[i]=1;
            }
else
            {
                d[i]=1000000001.0;
                step[i]=1000000001;
            }
        }
while(front!=rear)
        {
            u=q[front++];
            inq[u]=0;
if(front>N)
                front=0;
for(v=0;v<N;v++)
if(u!=v&&dis(u,v)<D+1e-7)
                {
                    temp=d[u]+dis(u,v);
if(temp<d[v]-1e-7)
                    {
                        d[v]=temp;
                        step[v]=step[u]+1;
if(!inq[v])
                        {
                            q[rear++]=v;
                            inq[v]=1;
if(rear>N)
                                rear=0;
                        }
                    }
if(fabs(temp-d[v])<1e-7&&step[u]+1<step[v])
                    {
                        step[v]=step[u]+1;
if(!inq[v])
                        {
                            q[rear++]=v;
                            inq[v]=1;
if(rear>N)
                                rear=0;
                        }
                    }
                }
        }
        memset(reach,0,sizeof(reach));
for(i=0;i<N;i++)
        {
            temp=fabs(x[i]+50.0);
if(fabs(x[i]-50.0)<temp)
                temp=fabs(x[i]-50);
if(fabs(y[i]+50.0)<temp)
                temp=fabs(y[i]+50);
if(fabs(y[i]-50)<temp)
                temp=fabs(y[i]-50);
if(temp<D+1e-7)
                reach[i]=1;
            d[i]+=temp;
            step[i]++;
        }
        ans_d=1000000001.0;
        ans_s=1000000001;
for(i=0;i<N;i++)
if(reach[i])
            {
if(d[i]<ans_d-1e-7)
                {
                    ans_d=d[i];
                    ans_s=step[i];
                }
if(fabs(d[i]-ans_d)<1e-7&&step[i]<ans_s)
                    ans_s=step[i];
            }
if(ans_d<1000000000.0)
            printf("%.2f %d\n",ans_d,ans_s);
else
            printf("can't be saved\n");
    }
return 0;    
}