hdu 1245 Saving James Bond

http://acm.hdu.edu.cn/showproblem.php?pid=1245

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <cmath>

  4 #include <queue>

  5 #include <algorithm>

  6 #define maxn 500

  7 using namespace std;

  8 const double inf=99999999.0;

  9 

 10 int n,m;

 11 double d;

 12 double g[maxn][maxn];

 13 double dis[maxn];

 14 bool vis[maxn];

 15 int step[maxn*4];

 16 struct node

 17 {

 18    int x,y;

 19 }p[maxn];

 20 

 21 double min(double x,double y)

 22 {

 23     if(x>y) return y;

 24     return x;

 25 }

 26 

 27 double sqr(int x)

 28 {

 29     return x*x;

 30 }

 31 

 32 double dist(int x1,int y1,int x2,int y2)

 33 {

 34     return sqrt(sqr(x1-x2)+sqr(y1-y2));

 35 }

 36 

 37 

 38 void spfa()

 39 {

 40     queue<int>q;

 41     memset(vis,false,sizeof(vis));

 42     for(int i=0; i<=n+1; i++)

 43     {

 44         dis[i]=inf;

 45     }

 46     dis[0]=0.0;

 47     vis[0]=true;

 48     step[0]=0;

 49     q.push(0);

 50     while(!q.empty())

 51     {

 52         int u=q.front(); q.pop();

 53         vis[u]=false;

 54         for(int i=1; i<=n+1; i++)

 55         {

 56             if(g[u][i]<=d)

 57             {

 58                 if(g[u][i]+dis[u]<dis[i])

 59                 {

 60                     dis[i]=dis[u]+g[u][i];

 61                     step[i]=step[u]+1;

 62                     if(!vis[i])

 63                     {

 64                         vis[i]=true;

 65                         q.push(i);

 66                     }

 67                 }

 68                 else if(g[u][i]+dis[u]==dis[i])

 69                 {

 70                     if(step[i]>step[u]+1)

 71                     {

 72                         step[i]=step[u]+1;

 73                         if(!vis[i])

 74                         {

 75                             vis[i]=true;

 76                             q.push(i);

 77                         }

 78                     }

 79                 }

 80             }

 81         }

 82     }

 83 }

 84 int main()

 85 {

 86     while(scanf("%d%lf",&n,&d)!=EOF)

 87     {

 88         for(int i=1; i<=n; i++)

 89         {

 90             scanf("%d%d",&p[i].x,&p[i].y);

 91         }

 92         for(int i=1; i<=n; i++)

 93         {

 94             g[i][i]=0.0;

 95             for(int j=1; j<=n; j++)

 96             {

 97                 g[i][j]=dist(p[i].x,p[i].y,p[j].x,p[j].y);

 98             }

 99         }

100         g[0][0]=0.0;

101         for(int i=1; i<=n; i++)

102         {

103             g[i][0]=0.0;

104             g[0][i]=dist(0,0,p[i].x,p[i].y)-7.5;

105         }

106         for(int i=1; i<=n; i++)

107         {

108             g[n+1][i]=0.0;

109             g[i][n+1]=min(50.0-fabs((double)p[i].x),50.0-fabs((double)p[i].y));

110         }

111         g[0][n+1]=inf;

112         spfa();

113         if(dis[n+1]==inf)

114             printf("can't be saved\n");

115         else

116             printf("%.2lf %d\n",dis[n+1],step[n+1]);

117     }

118     return 0;

119 }

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