Online JudgeProblem SetAuthorsOnline ContestsUser
Web Board
F.A.Qs
Statistical Charts
Problems
Submit Problem
Online Status
Prob.ID:
Register
Authors ranklist
Current Contest
Past Contests
Scheduled Contests
Award Contest
Register

## 将点排序，每次接着前面的往后找就行了，可是WA了一页，改成两层循环就过了。。。

Posted by AK47biubiubiu at 2017-01-10 09:40:43 on Problem 2318
```我的思路是直接将点排序，因为题目说线段是有序的，每次找点只需再上一次的基础上往下找就行了，怎么会错呢？
struct line
{
double x1,y1,x2,y2;
} a[N],b[N];
int v[N];
int cmp(line a,line b)
{
return a.x1<b.x1;
}
double multi(line b,line a)
{
return (a.x1-b.x1)*(a.y2-b.y1)-(a.x2-b.x1)*(a.y1-b.y1);
}
int main()
{
int n,m;
double x1,y1,x2,y2;
while(~scanf("%d",&n)&&n)
{
scanf("%d%lf%lf%lf%lf",&m,&x1,&y1,&x2,&y2);
memset(v,0,sizeof(v));
for(int i=1; i<=n; i++) //n条分界分成n+1个区域
{
scanf("%lf%lf",&a[i].x1,&a[i].x2);
a[i].y1=y1;
a[i].y2=y2;
}
a[0].x1=x1,a[0].y1=y1,a[0].x2=x1,a[0].y2=y2;//开始隔板
a[n+1].x1=x2,a[n+1].y1=y1,a[n+1].x2=x2,a[n+1].y2=y2;//最后一块区域
for(int i=0; i<m; i++) scanf("%lf%lf",&b[i].x1,&b[i].y1);
sort(b,b+m,cmp);
int j=0;
for(int i=0; i<m; i++)
{
//            while(multi(b[i],a[j])>0&&j<=n+1) j++;
//             j--;//用while一直WA，而改成下面的循环就过了。。
for(j=0; j<=n+1; j++)
if(multi(b[i],a[j])<0)
{
j--;
break;
}
v[j]++;
}
for(int i=0; i<=n; i++)
printf("%d: %d\n",i,v[i]);
printf("\n");
}
return 0;
}
```

Followed by: