Poj1410 cleverly turns a straight line into a line segment Intersection

This rough question is still considered to be the intersection of a line segment and a line segment, but the subject requires that the line segment is completely within the rectangle. Therefore, it can be changed to the intersection problem between the straight line of the target line segment a and each line segment of the rectangle, and then check whether the line segment a is within the rectangle range.

 

[Cpp]
# Include <iostream>
Using namespace std;
 
 
Struct Point
{
Point ()
{
X = 0.0f;
Y = 0.0f;
}
 
Point (double tx, double ty)
{
X = tx;
Y = ty;
}
 
Double x, y;
};
 
Struct Segment
{
Point point1, point2;
};
 
Double Min (double a, double B)
{
If (a <B)
Return;
Else
Return B;
}
 
Double Max (double a, double B)
{
If (a <B)
Return B;
Else
Return;
}
 
Double CrossProduct (Point vec1, Point vec2)
{
Return (vec1.x * vec2.y)-(vec1.y * vec2.x );
}
 
// Calculate the crossproduct of (P2-P1) * (p3-p1)
Double Direction (Point point1, Point point2, Point point3)
{
Point vec1;
Vec1.x = point2.x-point1.x;
Vec1.y = point2.y-point1.y;
 
Point vec2;
Vec2.x = point3.x-point1.x;
Vec2.y = point3.y-point1.y;
 
Return CrossProduct (vec1, vec2 );
}
 
// See if line interact the segment.
Bool LineInteractSegment (Segment line, Segment seg)
{
Point vec1;
Vec1.x = line. point2.x-line. point1.x;
Vec1.y = line. point2.y-line. point2.y;
 
Point vec2;
Vec2.x = seg. point2.x-seg. point1.x;
Vec2.y = seg. point2.y-seg. point2.y;
 
Double cross1 = CrossProduct (
Point (line. point2.x-line. point1.x, line. point2.y-line. point1.y ),
Point (seg. point1.x-line. point1.x, seg. point1.y-line. point1.y ));
 
Double cross2 = CrossProduct (
Point (line. point2.x-line. point1.x, line. point2.y-line. point1.y ),
Point (seg. point2.x-line. point1.x, seg. point2.y-line. point1.y ));
 
If (cross1 * cross2 <= 0)
Return true;
Else
Return false;
}
 
Bool SegmentInRect (Segment seg, Point leftTopPoint, Point rightBottomPoint)
{
Double minX = Min (seg. point1.x, seg. point2.x );
Double maxX = Max (seg. point1.x, seg. point2.x );
 
Double minY = Min (seg. point1.y, seg. point2.y );
Double maxY = Max (seg. point1.y, seg. point2.y );
 
If (minX> rightBottomPoint. x | maxX <leftTopPoint. x)
{
Return false;
}
Else
{
If (minY> leftTopPoint. y | maxY <rightBottomPoint. y)
{
Return false;
}
Else
{
Return true;
}
}
}
 
Void SwapData (double & a, double & B)
{
Double c =;
A = B;
B = c;
Return;
}
 
Int main ()
{
Bool HaveInteraction = false;
Segment seg;
Segment rectSeg [4];
Double leftTopX, leftTopY, rightBottomX, rightBottomY;
 
Int tCase;
// Cin> tCase;
Scanf ("% d", & tCase );
While (tCase> 0)
{
TCase --;
 
// Cin> seg. point1.x> seg. point1.y> seg. point2.x> seg. point2.y;
Scanf ("% lf", & seg. point1.x, & seg. point1.y, & seg. point2.x, & seg. point2.y );
 
// Cin> leftTopX> leftTopY> rightBottomX> rightBottomY;
Scanf ("% lf", & leftTopX, & leftTopY, & rightBottomX, & rightBottomY );
 
If (leftTopX> rightBottomX)
SwapData (leftTopX, rightBottomX );
If (rightBottomY> leftTopY)
SwapData (rightBottomY, leftTopY );
 
// Start from |, take turn in clockwise.
RectSeg [0]. point1 = Point (leftTopX, rightBottomY );
RectSeg [0]. point2 = Point (leftTopX, leftTopY );
 
RectSeg [1]. point1 = Point (leftTopX, leftTopY );
RectSeg [1]. point2 = Point (rightBottomX, leftTopY );
 
RectSeg [2]. point1 = Point (rightBottomX, leftTopY );
RectSeg [2]. point2 = Point (rightBottomX, rightBottomY );
 
RectSeg [3]. point1 = Point (rightBottomX, rightBottomY );
RectSeg [3]. point2 = Point (leftTopX, rightBottomY );
 
HaveInteraction = false;
For (int I = 0; I <4; I ++)
{
If (LineInteractSegment (seg, rectSeg [I]) // the line interact with the rectangle, see if the segment interact the rectangle too.
{
If (SegmentInRect (seg, Point (leftTopX, leftTopY), Point (rightBottomX, rightBottomY )))
{
// Cout <"T" <endl;
Printf ("T \ n ");
HaveInteraction = true;
}
Break;
}
}
 
If (HaveInteraction = false)
{
// Cout <"F" <endl;
Printf ("F \ n ");
}

}
 
Return 0;
}