[Swift]LeetCode302. 包含黑色像素的最小矩形 $ Smallest Rectangle Enclosing Black Pixels

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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An image is represented by a binary matrix with 0 as a white pixel and 1 as a black pixel. The black pixels are connected, i.e., there is only one black region. Pixels are connected horizontally and vertically. Given the location (x, y) of one of the black pixels, return the area of the smallest (axis-aligned) rectangle that encloses all black pixels.

For example, given the following image:

[
  "0010",
  "0110",
  "0100"
]

and x = 0, y = 2,

Return 6.

---

圖像由一個二進制矩陣表示，其中0爲白色像素，1爲黑色像素。黑色像素鏈接，即只有一個黑色區域。像素水平和垂直鏈接。給定一個黑色像素的位置(x, y)，返回包圍全部黑色像素的最小（軸對齊）矩形的區域。

例如，給出如下圖像：

[
  "0010",
  "0110",
  "0100"
]

X=0，Y=2，

返回6。

---

Solution:

 1 class Solution {
 2     func minArea(_ image:inout [String],_ x:Int,_ y:Int) -> Int {
 3         var m:Int = image.count
 4         var n:Int = image[0].count
 5         var up:Int = binary_search(&image, true, 0, x, 0, n, true)
 6         var down:Int = binary_search(&image, true, x + 1, m, 0, n, false)
 7         var left:Int = binary_search(&image, false, 0, y, up, down, true)
 8         var right:Int = binary_search(&image, false, y + 1, n, up, down, false)
 9         return (right - left) * (down - up)    
10     }
11     
12     // Binary Search
13     func binary_search(_ image:inout [String],_ h:Bool,_ i:Int,_ j:Int,_ low:Int,_ high:Int,_ opt:Bool) -> Int
14     {
15         var i = i 
16         var j = j
17         while (i < j)
18         {
19             var k:Int = low
20             var mid:Int = (i + j) / 2
21             while (k < high && (h ? image[mid][k] : image[k][mid]) == "0")
22             {
23                 k += 1
24             }
25             if (k < high) == opt{ j = mid }
26             else{ i = mid + 1 }
27         }
28         return i
29     }
30 }
31 
32 //String擴展
33 extension String {        
34     //subscript函數能夠檢索數組中的值
35     //直接按照索引方式截取指定索引的字符
36     subscript (_ i: Int) -> Character {
37         //讀取字符
38         get {return self[index(startIndex, offsetBy: i)]}
39     }
40 }

---

點擊：Playground測試

1 var sol = Solution()
2 var arr:[String] = ["0010","0110","0100"]
3 var x:Int = 0
4 var y:Int = 2
5 print(sol.minArea(&arr,x,y))
6 //Print 6