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【C】判断矩形相交
作者:G0561 / 发布于2013/4/16/ 800

	已知2矩形原点和宽高，判断2矩形相交，相交矩形

	相交判断原理：
	假定矩形是用一对点表达的(minx, miny) (maxx, maxy)，那么两个矩形
	 rect1{(minx1, miny1)(maxx1, maxy1)}
	 rect2{(minx2, miny2)(maxx2, maxy2)}
	相交的结果一定是个矩形，构成这个相交矩形rect{(minx, miny) (maxx, maxy)}的点对坐标是：
	 minx = max(minx1, minx2)
	 miny = max(miny1, miny2)
	 maxx = min(maxx1, maxx2)
	 maxy = min(maxy1, maxy2)
	
	如果两个矩形不相交，那么计算得到的点对坐标必然满足：
	 （ minx > maxx ） 或者 （ miny > maxy ）
	判定是否相交，以及相交矩形是什么都可以用这个方法一体计算完成


	设计3个类：
	1. 点类：x，y
	2. 矩形类：点，宽，高
	3. 判断相交类

	程序实现：
	CPoint.h
	#import <Foundation/Foundation.h>

	@interface CPoint : NSObject
	{
	 int x; //点坐标
	 int y;
	}
	-(void) print;
	-(void) setX: (int) vx;
	-(void) setY: (int) vy;
	-(void) setXY:(int) vx :(int) vy;
	-(int) x;
	-(int) y;

	@end

	CPoint.m
	#import "CPoint.h"

	@implementation CPoint

	-(void) print
	{
	 NSLog(@"the point is (%i, %i)",x,y);
	}

	-(void) setX: (int) vx
	{
	 x = vx;
	}

	-(void) setY: (int) vy
	{
	 y = vy;
	}

	-(void) setXY:(int)vx :(int)vy
	{
	 x = vx;
	 y = vy;
	}

	-(int) x
	{
	 return x;
	}

	-(int) y
	{
	 return y;
	}
	@end


	CRect.h
	#import <Foundation/Foundation.h>

	#import "CPoint.h"

	@interface CRect : NSObject
	{
	 int w; //矩形长
	 int h; //矩形高
	}

	-(void) print;
	-(int) w;
	-(int) h;
	-(void) setW: (int) vw;
	-(void) setH: (int) vh;
	-(void) setWH: (int) vw :(int) vh;
	-(CPoint *) origin;
	-(void) setOrigin: (CPoint *) pt;

	@end

	CRect.m
	#import "CRect.h"

	@implementation CRect
	{
	 CPoint *origin; //点
	}

	-(void) print
	{
	 NSLog(@"the rect:(x:%i, y:%i, w:%i,h:%i)",origin.x, origin.y, w, h);
	}

	-(int) w
	{
	 return w;
	}

	-(int) h
	{
	 return h;
	}

	-(void) setW:(int)vw
	{
	 w = vw;
	}

	-(void) setH:(int)vh
	{
	 h = vh;
	}

	-(void) setWH:(int)vw :(int)vh
	{
	 w = vw;
	 h = vh;
	}

	-(CPoint *) origin
	{
	 return origin;
	}

	-(void) setOrigin:(CPoint *)pt
	{
	 origin = pt;
	}
	@end

	DoCRect.h
	#import <Foundation/Foundation.h>

	#import "CRect.h"

	@interface DoCRect : NSObject

	-(BOOL) isIntersect:(CRect *) rect1 :(CRect *) rect2; //矩形相交否
	-(CRect *) intersectRect: (CRect *) rect1 :(CRect *) rect2; //相交矩形

	@end

	DoCRect.m

	#import "DoCRect.h"

	@implementation DoCRect

	//矩形是否相交
	-(BOOL) isIntersect:(CRect *)rect1 :(CRect *)rect2
	{
	 int minx = MAX(rect1.origin.x, rect2.origin.x);
	 int miny = MAX(rect1.origin.y, rect2.origin.y);
	 int maxx = MIN(rect1.origin.x+rect1.w, rect2.origin.x+rect2.w);
	 int maxy = MIN(rect1.origin.y+rect1.h, rect2.origin.y+rect2.h);
	
	 if (minx>maxx || miny>maxy)
	 {
	 return NO;
	 }
	 return YES;
	}

	-(CRect *) intersectRect:(CRect *)rect1 :(CRect *)rect2
	{
	 int minx = MAX(rect1.origin.x, rect2.origin.x);
	 int miny = MAX(rect1.origin.y, rect2.origin.y);
	 int maxx = MIN(rect1.origin.x+rect1.w, rect2.origin.x+rect2.w);
	 int maxy = MIN(rect1.origin.y+rect1.h, rect2.origin.y+rect2.h);
	
	 CRect * rect = [[CRect alloc] init];
	 CPoint *p = [[CPoint alloc] init];
	
	 if (NO == [self isIntersect:rect1 :rect2])//no isIntersect
	 {
	 [p setXY:minx :miny];
	 [rect setOrigin:p];
	 rect.w = 0;
	 rect.h = 0;
	 return rect;
	 }
	
	 [p setXY:minx :miny];
	 [rect setOrigin:p];
	 rect.w = ABS(maxx-minx);
	 rect.h = ABS(maxy - miny);
	 return rect;
	}

	@end

	main.m 测试

	#import <Foundation/Foundation.h>

	#import "DoCRect.h"

	int main(int argc, const char * argv[])
	{

	 @autoreleasepool
	 {
	 NSLog(@"Hello,判断矩形相交，返回矩形的原点和长高");
	
	 //初始化对象
	 CRect *myrect1 = [[CRect alloc] init];
	 CRect *myrect2 = [[CRect alloc] init];
	 CPoint *p1 = [[CPoint alloc] init];
	 CPoint *p2 = [[CPoint alloc] init];
	
	 DoCRect *dorect = [[DoCRect alloc] init];
	
	 //原点变量
	 [p1 setXY:200 :420];
	 [p2 setXY:400 :300];
	
	 //设置矩形原点
	 [myrect1 setOrigin:p1];
	 [myrect1 setWH:250 :75];
	 [myrect1 print];
	
	 [myrect2 setOrigin:p2];
	 [myrect2 setWH:100 :180];
	 [myrect2 print];
	
	 //判断2矩形是否相交
	 BOOL insersect = [dorect isIntersect:myrect1 :myrect1];
	 NSLog(@" two rect is :%@",insersect?@"YES":@"NO");
	
	 //返回相交矩形
	 //CRect *inserectRect = [[CRect alloc] init];
	 CRect *inserectRect = [dorect intersectRect:myrect1 :myrect2];
	 [inserectRect print];
	
	
	 }
	 return 0;
	}
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