POJ 1328 Radar Installation 贪心

#include"stdio.h" #include"math.h" #include"stdlib.h" typedef struct { double x1,x2; }POINT; int cmp(const void *a,const void *b) { return (*(POINT *)a).x1>(*(POINT *)b).x1?1:-1; } POINT t[1000]; main() { int n,d,ans,i=0,j,judge,tag; double tx,ty; while(scanf("%d%d",&n,&d)!=EOF&&(n||d)) { for(j=0,judge=0;j<n;j++) { scanf("%lf %lf",&tx,&ty); if(ty>d||d==0){judge=1;} if(!judge) { t[j].x1=tx-sqrt(d*d-ty*ty); t[j].x2=tx+sqrt(d*d-ty*ty); } } if(!judge)qsort(t,n,sizeof(POINT),cmp); ans=1,tag=0; for(j=1;!judge&&j<n;j++) if(t[j].x1>t[tag].x2)ans++,tag=j; else if(t[j].x2<t[tag].x2)tag=j; printf("Case %d: ",++i); if(!judge)printf("%d\n",ans); else puts("-1"); } return 0; }