貪心/poj 1328 Radar Installation

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 1 #include<cstdio> 2 #include<cstring> 3 #include<cmath> 4 #include<algorithm> 5 using namespace std; 6 struct node 7 { 8     double right,left; 9 };10 node a[1010];11 int ans,n,d;12 bool flag;13 14 bool cmp(node x,node y)15 {16     return x.left<y.left;17 }18 19 int main()20 {21     int T=0;22     scanf("%d%d",&n,&d);23     while (n!=0)24     {25         T++;26         flag=true;27         ans=0;28         memset(a,0,sizeof(a));29         for (int i=1;i<=n;i++)30         {31             int xx,yy;32             scanf("%d%d",&xx,&yy);33             if (yy>d)34             {35                 flag=false;36                 continue;37             }38             double dx=sqrt(d*d-yy*yy);39             a[i].left=xx-dx;40             a[i].right=xx+dx;41         }42         if (flag==false) ans=-1;43         else44         {45             sort(a+1,a+n+1,cmp);46             double last=a[1].right;47             ans=1;48             for (int i=2;i<=n;i++)49             {50                 if (a[i].left>last)51                 {52                     ans++;53                     last=a[i].right;54                 }55                 else if (a[i].right<last) last=a[i].right;56             }57         }58         printf("Case %d: %d\n",T,ans);59         scanf("%d%d",&n,&d);60     }61     return 0;62 }

 

貪心/poj 1328 Radar Installation