我大哥說過，【沒有一種演算法是脫離實際問題而存在的。】
於是，當我遇到這個問題時候，我知道計算機理論上學的演算法都不能解決這個問題，我需要靈活運用。

例1

例2

專案中遇到這麼一個棘手的問題，要根據網路獲取的實時資料，把同一工序的狀態畫虛線框起來。
也不算是個很困難的問題，但是還是有一定的複雜度，經過一晚上思考，找到了一種比較好的演算法。

相信看完了圖片，大家發現了這個演算法的核心所在——就是每一行上面的4個輔助點。所包含的範圍起始分解一下就是n個矩形，然後根據矩形的4個角的點，連線即可。

所以，步驟就有了：
第一步：根據給定的起始圓圈和終止圓圈，找出所有選中的圓圈 放在selectedArr中
第二部：便利selectedArr，找出每一行的最左邊和最右邊的圓圈，分別放進leftProviews和rightProviews陣列中，為了取四角的座標值用
第三部：左邊的座標依次連線，右邊的座標依次連線，最有把最頂上和最底下兩個座標相連，一個虛線框就出來了。

【圓圈是ProcessView：UIButton】
為了方便我判斷行列，我繼承UIButton，給button添加了row和count兩個屬性
@row:行
@count:順序(這裡之所以不用cow列來表示，是因為隔行的圓圈順序排列是相反的，有的從左到右，有的從右到左)

/**
 給定起始圓圈和結束圓圈 找圓圈陣列，找矩形，最後畫線框
 @param start 開始圓圈
 @param end   結束圓圈
 */
-(void)DrawDashLineRectStart:(ProcessView *)start end:(ProcessView *)end{

    // 畫之前先清除之前的虛線
 

    NSArray *sublayers = [NSArray arrayWithArray:self.contentView.layer.sublayers];
    for (CALayer *ly in sublayers) {
        if ([ly isKindOfClass:[XLShapeLayer class]]) {
            XLShapeLayer *xlL = (XLShapeLayer *)ly;
            if (xlL.tag == 999) {
                [xlL removeFromSuperlayer];
            }
        }
    }

    NSMutableArray *selectedArr = [NSMutableArray new
 
];
    for (short i = start.row; i<=end.row; i++) {
        for (short j = 0; j<6; j++) {
            if(i == start.row && j < start.count) continue;
            if (i == end.row && j > end.count)  break;
            ProcessView *pro = (ProcessView *)[self.contentView viewWithTag:60+(i*6+j)];
            [selectedArr addObject:pro];
            //DLog(@"pro:%ld %ld", pro.row, pro.count);
            //DLog(@"%@",pro.titleLabel.text);
        }
    }
    // 列印該被選中的陣列
    //DLog(@"Pro:%@",selectedArr);

    // 分出左右陣列 左陣列存放左邊的點依賴的圓圈 右陣列同理。
    NSMutableArray *leftPros = [NSMutableArray new];
    NSMutableArray *rightPros = [NSMutableArray new];
    for (ProcessView *pro in selectedArr) {
        if (end.row > start.row) {
            if (pro.row%2==0) {
                if ((pro.count==0) || pro==start) {
                    [leftPros addObject:pro];
                }
                if (pro.count == 5 || pro==end) {
                    [rightPros addObject:pro];
                }

            }
            if (pro.row%2==1) {
                if ((pro.count==0 || pro == start)) {
                    [rightPros addObject:pro];
                }
                if (pro.count==5 || pro==end) {
                    [leftPros addObject:pro];
                }

            }
        }else{
            if (end.row%2==0) {
                [leftPros addObject:start];
                [rightPros addObject:end];
            }else{
                [leftPros addObject:end];
                [rightPros addObject:start];
            }
            break;
        }
    }

    /*  // 左右陣列資訊列印
    for (short i =0; i<leftPros.count; i++) {
        ProcessView *p = leftPros[i];
        DLog(@"L:%@",p.titleLabel.text);
    }
    for (short i =0; i<rightPros.count; i++) {
        ProcessView *p = rightPros[i];
        DLog(@"R:%@",p.titleLabel.text);
    }
     */

    // 根據左右陣列，找到左邊的所有點 和右邊的所有點 然後依次相連
    // spc是實際的點與圓圈frame的偏移量，因為虛線要離開圓圈一段距離
    NSMutableArray *leftPoints = [NSMutableArray new];
    NSMutableArray *rightPoints = [NSMutableArray new];
    CGAffineTransform lastTransform;
    for (ProcessView *pro in leftPros) {
        lastTransform = pro.layer.affineTransform;
        pro.layer.affineTransform = pro->affineTransform;
        CGPoint start = CGPointMake(pro.frame.origin.x-spc/2., pro.frame.origin.y-spc/2.);
        CGPoint end = CGPointMake(start.x, CGRectGetMaxY(pro.frame)+spc/2.);
        [leftPoints addObject:NSStringFromCGPoint(start)];
        [leftPoints addObject:NSStringFromCGPoint(end)];
        pro.layer.affineTransform = lastTransform;
    }
    for (ProcessView *pro in rightPros) {
        lastTransform = pro.layer.affineTransform;
        pro.layer.affineTransform = pro->affineTransform;
        CGPoint start = CGPointMake(CGRectGetMaxX(pro.frame)+spc/2., pro.frame.origin.y-spc/2.);
        CGPoint end = CGPointMake(start.x, CGRectGetMaxY(pro.frame)+spc/2.);
        [rightPoints addObject:NSStringFromCGPoint(start)];
        [rightPoints addObject:NSStringFromCGPoint(end)];
        pro.layer.affineTransform = lastTransform;
    }

    //左邊的點連線
    for (short i=leftPoints.count-1; i>0; i--) {
        CGPoint start = CGPointFromString(leftPoints[i]);
        CGPoint end = CGPointFromString(leftPoints[i-1]);
        [self drawDashLineStart:start end:end];
    }
    //右邊的點連線    
    for (short i=rightPoints.count-1; i>0; i--) {
        CGPoint start = CGPointFromString(rightPoints[i]);
        CGPoint end = CGPointFromString(rightPoints[i-1]);
        [self drawDashLineStart:start end:end];
    }

    // 頂上和地下的點連線
    CGPoint topL = CGPointFromString(leftPoints[0]);
    CGPoint topR = CGPointFromString(rightPoints[0]);
    CGPoint btmL = CGPointFromString([leftPoints lastObject]);
    CGPoint btmR = CGPointFromString([rightPoints lastObject]);
    [self drawDashLineStart:topL end:topR];
    [self drawDashLineStart:btmL end:btmR];
}

畫虛線的方法，用CAShapeLayer即可

/**
 給定起點 重點畫虛線

 @param start 起點座標
 @param end   終點座標
 */
- (void)drawDashLineStart:(CGPoint)start end:(CGPoint)end{
    //NSLog(@"%@",NSStringFromCGRect(lineView.frame));

    XLShapeLayer *shapeLayer = [XLShapeLayer layer];
    shapeLayer.tag = 999;
    [shapeLayer setBounds:self.contentView.bounds];
    [shapeLayer setPosition:CGPointMake(CGRectGetWidth(self.contentView.frame)/2.f, CGRectGetHeight(self.contentView.frame)/2.f)];
    [shapeLayer setFillColor:[[UIColor clearColor] CGColor]];
    // 設定虛線顏色為blackColor [shapeLayer setStrokeColor:[[UIColor blackColor] CGColor]];
    [shapeLayer setStrokeColor:KLIGHTGRAYCOLOR.CGColor];
    // 3.0f設定虛線的寬度 [shapeLayer setLineWidth:1.0f];
    [shapeLayer setLineJoin:kCALineJoinRound];
    // 3=線的寬度 1=每條線的間距 [shapeLayer setLineDashPattern:
    [shapeLayer setLineDashPattern:[NSArray arrayWithObjects:[NSNumber numberWithInt:1],[NSNumber numberWithInt:3],nil]];
    // Setup the path CGMutablePathRef path = CGPathCreateMutable();
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, start.x, start.y);
    CGPathAddLineToPoint(path, NULL, end.x,end.y);

    [shapeLayer setPath:path];
    CGPathRelease(path);
    [self.contentView.layer addSublayer:shapeLayer];
}