POJ 2653
开一个数组做成队列来搜索就好了。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <queue> 5 #include <algorithm> 6 using namespace std; 7 8 const int MAXN=100010; 9 10 typedef struct po{ 11 double x,y; 12 }Point; 13 struct e{ 14 Point start,end; 15 }edge[MAXN],ss,ee; 16 int n; 17 double x1,y1,x2,y2; 18 Point start,end; 19 int que[MAXN*100]; 20 21 double multi(Point p1, Point p2, Point p0){ 22 return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y); 23 } 24 25 bool slove(int k,int i){ 26 ss=edge[k]; ee=edge[i]; 27 if(max(ss.start.x,ss.end.x)>=min(ee.start.x,ee.end.x)&& 28 max(ee.start.x,ee.end.x)>=min(ss.start.x,ss.end.x)&& 29 max(ss.start.y,ss.end.y)>=min(ee.start.y,ee.end.y)&& 30 multi(ee.start,ss.end,ss.start)*multi(ss.end,ee.end,ss.start)>0&& 31 multi(ss.start,ee.end,ee.start)*multi(ee.end,ss.end,ee.start)>0){ 32 return true; 33 } 34 return false; 35 } 36 37 int main(){ 38 int f,l; 39 while(scanf("%d",&n)!=EOF){ 40 if(n==0) break; f=l=0; 41 for(int i=1;i<=n;i++){ 42 scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2); 43 start.x=x1; start.y=y1; 44 end.x=x2; end.y=y2; 45 edge[i].start=start; edge[i].end=end; 46 if(i>1){ 47 int size=l-f; 48 while(size--){ 49 int k=que[f++]; 50 if(!slove(k,i)) 51 que[l++]=k; 52 } 53 } 54 que[l++]=i; 55 } 56 bool flag=false; 57 printf("Top sticks:"); 58 while(f<l){ 59 int i=que[f++]; 60 if(!flag){ 61 printf(" %d",i); 62 flag=true; 63 } 64 else{ 65 printf(", %d",i); 66 } 67 } 68 printf(".\n"); 69 } 70 return 0; 71 }
