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package
{
import
flash.display.Sprite;
import
flash.events.MouseEvent;
import
flash.text.TextField;
[SWF(width=
375
,height=
300
,backgroundColor=
"0xeeeeee"
)]
public
class
RectLine
extends
Sprite
{
private
var
txt:TextField;
public
function
RectLine()
{
this
.txt =
new
TextField();
addChild(txt);
stage.addEventListener(MouseEvent.CLICK,ckHandler);
ckHandler(
null
);
}
private
function
ckHandler(e:MouseEvent):
void
{
graphics.clear();
graphics.beginFill(
0x00ffff
);
graphics.drawRect(
100
,
100
,
200
,
50
);
graphics.endFill();
var
a:
int
= Math.random()*
375
;
var
b:
int
= Math.random()*
300
;
var
c:
int
= Math.random()*
375
;
var
d:
int
= Math.random()*
300
;
graphics.lineStyle(
2
,
0xff0000
);
graphics.moveTo(a,b);
graphics.lineTo(c,d);
trace
(isLineIntersectRectangle(a,b,c,d,
100
,
100
,
300
,
150
));
var
isF:
Boolean
= isLineIntersectRectangle(a,b,c,d,
100
,
100
,
300
,
150
);
txt.text =
"是否相交："
+isF;
}
/** <p>判断线段是否在矩形内 </p>
* 先看线段所在直线是否与矩形相交，
* 如果不相交则返回false，
* 如果相交，
* 则看线段的两个点是否在矩形的同一边（即两点的x(y)坐标都比矩形的小x(y)坐标小，或者大）,
* 若在同一边则返回false，
* 否则就是相交的情况。
* @param linePointX1 线段起始点x坐标
* @param linePointY1 线段起始点y坐标
* @param linePointX2 线段结束点x坐标
* @param linePointY2 线段结束点y坐标
* @param rectangleLeftTopX 矩形左上点x坐标
* @param rectangleLeftTopY 矩形左上点y坐标
* @param rectangleRightBottomX 矩形右下点x坐标
* @param rectangleRightBottomY 矩形右下点y坐标
* @return 是否相交
*/
private
function
isLineIntersectRectangle(linePointX1:
Number
,
linePointY1:
Number
,
linePointX2:
Number
,
linePointY2:
Number
,
rectangleLeftTopX:
Number
,
rectangleLeftTopY:
Number
,
rectangleRightBottomX:
Number
,
rectangleRightBottomY:
Number
):
Boolean
{
var
lineHeight:
Number
= linePointY1 - linePointY2;
var
lineWidth:
Number
= linePointX2 - linePointX1;
// 计算叉乘
var
c:
Number
= linePointX1 * linePointY2 - linePointX2 * linePointY1;
if
((lineHeight * rectangleLeftTopX + lineWidth * rectangleLeftTopY + c >=
0
&& lineHeight * rectangleRightBottomX + lineWidth * rectangleRightBottomY + c <=
0
)
|| (lineHeight * rectangleLeftTopX + lineWidth * rectangleLeftTopY + c <=
0
&& lineHeight * rectangleRightBottomX + lineWidth * rectangleRightBottomY + c >=
0
)
|| (lineHeight * rectangleLeftTopX + lineWidth * rectangleRightBottomY + c >=
0
&& lineHeight * rectangleRightBottomX + lineWidth * rectangleLeftTopY + c <=
0
)
|| (lineHeight * rectangleLeftTopX + lineWidth * rectangleRightBottomY + c <=
0
&& lineHeight * rectangleRightBottomX + lineWidth * rectangleLeftTopY + c >=
0
))
{
if
(rectangleLeftTopX > rectangleRightBottomX) {
var
temp:
Number
= rectangleLeftTopX;
rectangleLeftTopX = rectangleRightBottomX;
rectangleRightBottomX = temp;
}
if
(rectangleLeftTopY < rectangleRightBottomY) {
var
temp1:
Number
= rectangleLeftTopY;
rectangleLeftTopY = rectangleRightBottomY;
rectangleRightBottomY = temp1; }
if
((linePointX1 < rectangleLeftTopX && linePointX2 < rectangleLeftTopX)
|| (linePointX1 > rectangleRightBottomX && linePointX2 > rectangleRightBottomX)
|| (linePointY1 > rectangleLeftTopY && linePointY2 > rectangleLeftTopY)
|| (linePointY1 < rectangleRightBottomY && linePointY2 < rectangleRightBottomY)) {
return
false
;
}
else
{
return
true
;
}
}
else
{
return
false
;
}
}
}
}
|
http://blog.sqstudio.com/as3/algorithm/842.html#codesyntax_1
本文转自jiahuafu博客园博客，原文链接http://www.cnblogs.com/jiahuafu/p/4024661.html如需转载请自行联系原作者
jiahuafu
![P3842 [TJOI2007]线段(经典DP)](https://ucc.alicdn.com/pic/developer-ecology/5e462ba5d8d3400988fe236be4945550.png?x-oss-process=image/resize,h_160,m_lfit)