poj 1410 线段相交判断
http://poj.org/problem?id=1410
Time Limit: 1000MS | Memory Limit: 10000K | |
Total Submissions: 11329 | Accepted: 2978 |
Description
An example:
line: start point: (4,9)
end point: (11,2)
rectangle: left-top: (1,5)
right-bottom: (7,1)
Figure 1: Line segment does not intersect rectangle
The line is said to intersect the rectangle if the line and the rectangle have at least one point in common. The rectangle consists of four straight lines and the area in between. Although all input values are integer numbers, valid intersection points do not have to lay on the integer grid.
Input
xstart ystart xend yend xleft ytop xright ybottom
where (xstart, ystart) is the start and (xend, yend) the end point of the line and (xleft, ytop) the top left and (xright, ybottom) the bottom right corner of the rectangle. The eight numbers are separated by a blank. The terms top left and bottom right do not imply any ordering of coordinates.
Output
Sample Input
1
4 9 11 2 1 5 7 1
Sample Output
F
Source
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <math.h> using namespace std;
typedef struct point
{
int x,y;
}point; typedef struct line
{
point st,ed;
}line; int crossProduct(point a,point b,point c)
{
return (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);
} bool onSegment(point a,point b,point c)
{
int maxx=max(a.x,b.x);
int maxy=max(a.y,b.y);
int minx=min(a.x,b.x);
int miny=min(a.y,b.y);
if(crossProduct(a,b,c)==&&(c.x<=maxx)&&(c.x>=minx)&&(c.y<=maxy)&&(c.y>=miny))
{
return true;
}
return false;
} bool segIntersect(point p1,point p2,point p3,point p4)
{
int d1=crossProduct(p3,p4,p1);
int d2=crossProduct(p3,p4,p2);
int d3=crossProduct(p1,p2,p3);
int d4=crossProduct(p1,p2,p4);
if(d1*d2< && d3*d4<)
return true;
if(d1== && onSegment(p3,p4,p1))
return true;
if(d2== && onSegment(p3,p4,p2))
return true;
if(d3== && onSegment(p1,p2,p3))
return true;
if(d4== && onSegment(p1,p2,p4))
return true;
return false;
} point p[];
line li[];
int num[]; int main()
{
int n,m,i,j;
line tmp;
int xleft,ytop,xright,ybottom;
scanf("%d",&n);
while(n--)
{
scanf("%d%d%d%d%d%d%d%d",&tmp.st.x,&tmp.st.y,&tmp.ed.x,&tmp.ed.y
,&xleft,&ytop,&xright,&ybottom);
li[].st.x=xleft;
li[].st.y=ytop;
li[].ed.x=xleft;
li[].ed.y=ybottom; li[].st.x=xleft;
li[].st.y=ybottom;
li[].ed.x=xright;
li[].ed.y=ybottom; li[].st.x=xright;
li[].st.y=ybottom;
li[].ed.x=xright;
li[].ed.y=ytop; li[].st.x=xright;
li[].st.y=ytop;
li[].ed.x=xleft;
li[].ed.y=ytop; bool flag=true;
for(i=;i<;i++)
{
if(segIntersect(tmp.st,tmp.ed,li[i].st,li[i].ed))
{
flag=false;
break;
}
} int maxx=max(xleft,xright);
int maxy=max(ytop,ybottom);
int minx=min(xleft,xright);
int miny=min(ytop,ybottom);
if(tmp.st.x<=maxx&&tmp.st.x>=minx&&tmp.st.y>=miny&&tmp.st.y<=maxy
||tmp.ed.x<=maxx&&tmp.ed.x>=minx&&tmp.ed.y>=miny&&tmp.ed.y<=maxy)
flag=false; if(flag)
printf("F\n");
else printf("T\n");
}
return ;
}
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