[Swift]LeetCode947. 移除最多的同行或同列石头 | Most Stones Removed with Same Row or Column

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➤微信公众号：山青咏芝（shanqingyongzhi）
➤博客园地址：山青咏芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：https://www.cnblogs.com/strengthen/p/10015292.html
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On a 2D plane, we place stones at some integer coordinate points. Each coordinate point may have at most one stone.

Now, a move consists of removing a stone that shares a column or row with another stone on the grid.

What is the largest possible number of moves we can make?

Example 1:

Input: stones = [[0,0],[0,1],[1,0],[1,2],[2,1],[2,2]]
Output: 5

Example 2:

Input: stones = [[0,0],[0,2],[1,1],[2,0],[2,2]]
Output: 3

Example 3:

Input: stones = [[0,0]]
Output: 0

Note:

1 <= stones.length <= 1000
0 <= stones[i][j] < 10000

在二维平面上，我们将石头放置在一些整数坐标点上。每个坐标点上最多只能有一块石头。

现在，move 操作将会移除与网格上的另一块石头共享一列或一行的石头。

我们最多能执行多少次 move 操作？

示例 1：

输入：stones = [[0,0],[0,1],[1,0],[1,2],[2,1],[2,2]]
输出：5

示例 2：

输入：stones = [[0,0],[0,2],[1,1],[2,0],[2,2]]
输出：3

示例 3：

输入：stones = [[0,0]]
输出：0

提示：

1 <= stones.length <= 1000
0 <= stones[i][j] < 10000

272ms

  1 class Solution {
  2         class Coordinate:Hashable{
  3             static func == (lhs: Coordinate, rhs: Coordinate) -> Bool {
  4                 return lhs.x == rhs.x && lhs.y == rhs.y;
  5             }
  6             
  7             let x:Int;
  8             let y:Int;
  9             init(x:Int,y:Int) {
 10                 self.x = x;
 11                 self.y = y;
 12             }
 13             var hashValue:Int{
 14                 return x.hashValue ^ y.hashValue;
 15             }
 16         }
 17         class Vertex:Hashable,Comparable{
 18             var hashValue:Int{
 19                 get{
 20                     return co.hashValue;
 21                 }
 22             }
 23             static func < (lhs: Vertex, rhs: Vertex) -> Bool {
 24                 return lhs.degree < rhs.degree;
 25             }
 26             
 27             static func == (lhs: Vertex, rhs: Vertex) -> Bool {
 28                 return lhs.co == rhs.co;
 29             }
 30             let co:Coordinate;
 31             var neighbors:Set<Vertex>;
 32             var degree:Int{
 33                 get {
 34                     return neighbors.count;
 35                 }
 36             }
 37             var traversed:Bool;
 38             init(x:Int,y:Int) {
 39                 self.co = Coordinate(x: x, y: y);
 40                 neighbors = Set<Vertex>();
 41                 traversed = false;
 42             }
 43         }
 44         var max = 0;
 45         func removeStones(_ stones: [[Int]]) -> Int {
 46             max = 0;
 47             if stones.count < 2{
 48                 return 0;
 49             }
 50             var allStones = Dictionary<Coordinate,Vertex>();
 51             var xDict = Dictionary<Int,Array<Coordinate>>();
 52             var yDict = Dictionary<Int,Array<Coordinate>>();
 53             for stone in stones{
 54                 let x = stone[0];
 55                 let y = stone[1];
 56                 let co = Coordinate(x: x, y: y);
 57                 let vertex = Vertex(x: x, y: y);
 58                 allStones[co] = vertex;
 59                 if xDict[x] == nil{
 60                     xDict[x] = Array<Coordinate>()
 61                 }
 62                 if yDict[y] == nil{
 63                     yDict[y] = Array<Coordinate>()
 64                 }
 65                 xDict[x]!.append(co);
 66                 yDict[y]!.append(co);
 67             }
 68             
 69             for coco in allStones.keys{
 70                 let v = allStones[coco]!;
 71                 let x = coco.x;
 72                 let y = coco.y;
 73 //                let keys = allStones.keys;
 74                 var leftClosest:Coordinate?
 75                 var rightClosest:Coordinate?
 76                 var topClosest:Coordinate?
 77                 var bottomClosest:Coordinate?
 78                 for c in xDict[x]!{
 79                     if c.y != y{
 80                         if c.y < y{
 81                             if topClosest == nil || topClosest!.y < c.y{
 82                                 topClosest = c;
 83                             }
 84                         }else{
 85                             if bottomClosest == nil || bottomClosest!.y > c.y{
 86                                 bottomClosest = c;
 87                             }
 88                         }
 89                     }
 90                 }
 91                 for c in yDict[y]!{
 92                     if c.x != x{
 93                         if c.x < x{
 94                             if leftClosest == nil || leftClosest!.x < c.x{
 95                                 leftClosest = c;
 96                             }
 97                         }else{
 98                             if rightClosest == nil || rightClosest!.y > c.y{
 99                                 rightClosest = c;
100                             }
101                         }
102                     }
103                 }
104                 if leftClosest != nil{
105                     v.neighbors.insert(allStones[leftClosest!]!)
106                 }
107                 if rightClosest != nil{
108                     v.neighbors.insert(allStones[rightClosest!]!)
109                 }
110                 if topClosest != nil{
111                     v.neighbors.insert(allStones[topClosest!]!)
112                 }
113                 if bottomClosest != nil{
114                     v.neighbors.insert(allStones[bottomClosest!]!)
115                 }
116             }
117             for v in allStones.values{
118                 let n = dfs(vertex: v) - 1;
119                 if n > 0{
120                     max += n;
121                 }
122             }
123             return max;
124         }
125         func dfs(vertex:Vertex) -> Int {
126             if vertex.traversed{
127                 return 0;
128             }else{
129                 var sum = 1;
130                 vertex.traversed = true;
131                 for v in vertex.neighbors{
132                     sum += dfs(vertex: v);
133                 }
134                 return sum;
135             }
136         }
137     }

316ms

 1 class Solution {
 2     func removeStones(_ stones: [[Int]]) -> Int {
 3         guard stones.count > 0 else {
 4             return 0
 5         }
 6         var v = [Int](repeating: 0, count: stones.count)
 7         var dr = [Int: [Int]]()
 8         var dc = [Int: [Int]]()
 9         for i in 0 ..< stones.count {
10             let s = stones[i]
11             dr[s[1], default: [Int]()].append(i)
12             dc[s[0], default: [Int]()].append(i)
13         }
14         func bfs(_ i: Int) {
15             var qs = [stones[i]]
16             while !qs.isEmpty {
17                 //print(v)
18                 let u = qs.remove(at: 0)
19                 let rs = dr[u[1], default: [Int]()]
20                 let cs = dc[u[0], default: [Int]()]
21                 var d = [Int: Bool]()
22                 let ns = rs + cs
23                 for n in ns {
24                     d[n] = true
25                 }
26                 let ks = Array(d.keys)
27                 for k in ks {
28                     if v[k] != 2 {
29                         v[k] += 1
30                     }
31                 }
32                 qs += ks.filter {v[$0] == 1}.map {stones[$0]}
33             }
34         }
35         var res = 0
36         for i in 0 ..< stones.count {
37             guard v[i] != 2 else {
38                 continue
39             }
40             res += 1
41             bfs(i)
42         }
43         return stones.count - res
44 
45     }
46 }

1284ms

 1 class Solution {
 2     func removeStones(_ stones: [[Int]]) -> Int {        
 3         
 4         let unionFind = UnionFind(stones.count)
 5         for i in 0..<stones.count-1 {
 6             for j in i+1..<stones.count {
 7                 if stones[i][0] == stones[j][0] || 
 8                    stones[i][1] == stones[j][1] {
 9                     unionFind.union(i, j)
10                 }
11             }
12         }
13         
14         var counter = 0
15         for i in 0..<unionFind.root.count {
16             if unionFind.root[i] != i {
17                 counter += 1
18             }
19         }
20         return counter
21     }
22 }
23 
24 class UnionFind {
25     var root = [Int]()
26     var rank = [Int]()
27     
28     public init(_ n: Int) {
29          // if root is not initialized, 'self' captured by a closure before all members were initialized
30         (0...n-1).forEach { root.append($0) }
31         rank = [Int](repeating: 1, count: n)
32     }
33         
34     fileprivate func find(_ current: Int) -> Int {
35         var path = [Int]()
36         var current = current
37         while root[current] != current {
38             path.append(current)
39             current = root[current]
40         }
41         
42         for p in path {
43             root[p] = current
44         }
45         return current
46     }
47     
48     public func union(_ x: Int, _ y: Int) {
49         let xRoot = find(x)
50         let yRoot = find(y)
51         
52         if xRoot == yRoot {
53             return
54         }
55         if rank[xRoot] > rank[yRoot] {
56             root[yRoot] = xRoot
57         } else if rank[xRoot] < rank[yRoot] {
58             root[xRoot] = yRoot
59         } else {
60             rank[xRoot] = root[xRoot] + 1
61             root[xRoot] = yRoot
62         }
63     }
64 }

1436ms

 1 class Solution {
 2     func removeStones(_ stones: [[Int]]) -> Int {
 3         var n:Int = stones.count
 4         var ds:DJSet = DJSet(n)
 5         for i in 0..<n
 6         {
 7             for j in (i + 1)..<n
 8             {
 9                 if stones[i][0] == stones[j][0] || stones[i][1] == stones[j][1]
10                 {
11                     ds.union(i, j)
12                 }
13             }
14         }
15         return n-ds.count()
16     }
17 }
18 
19 public class DJSet 
20 {
21     var upper:[Int] = [Int]()
22     
23     public init(_ n:Int)
24     {
25         upper = [Int](repeating:-1,count: n)
26     }
27     
28     public func root(_ x:Int) -> Int
29     {
30         if upper[x] < 0
31         {
32             return x
33         }
34         else
35         {
36             upper[x] = root(upper[x])
37             return upper[x]
38         }
39     }
40     
41     public func equiv(_ x:Int,_ y:Int) -> Bool
42     {
43         return root(x) == root(y)
44     }
45     
46     public func union(_ x:Int,_ y:Int) -> Bool
47     {
48         var x:Int = root(x)
49         var y:Int = root(y)
50         if (x != y)
51         {
52             if (upper[y] < upper[x]) 
53             {
54                 var d:Int = x
55                 x = y
56                 y = d
57             }
58             upper[x] += upper[y]
59             upper[y] = x
60         }
61         return x == y
62     }
63 
64     public func count()-> Int 
65     {
66         var ct:Int = 0
67         for u in upper
68         {
69             if u < 0
70             {
71                 ct += 1
72             }
73         }
74         return ct
75     }
76 }

1476ms

  1 class Solution {
  2     func removeStones(_ stones: [[Int]]) -> Int {
  3         
  4         var xPointsMap:[Int:[[Int]]] = [:]
  5         var yPointsMap:[Int:[[Int]]] = [:]
  6         var xTag:[Int:Int] = [:]
  7         var yTag:[Int:Int] = [:]
  8         
  9         // merge by x and y
 10         for stone in stones {
 11             
 12             let x = stone[0]
 13             let y = stone[1]
 14             if let _ = xPointsMap[x] {
 15                 xPointsMap[x]!.append(stone)
 16             } else {
 17                 xPointsMap[x] = [stone]
 18             }
 19             
 20             if let _ = yPointsMap[y] {
 21                 yPointsMap[y]!.append(stone)
 22             } else {
 23                 yPointsMap[y] = [stone]
 24             }
 25         }
 26         
 27         // init x tags and y tags
 28         for (x,_) in xPointsMap {
 29             xTag[x] = 0
 30         }
 31         for (y,_) in yPointsMap {
 32             yTag[y] = 0
 33         }
 34         
 35         var totalMove = 0
 36         
 37         var currentTag = 1
 38         while true {
 39             var startX:Int?
 40             for (x,tag) in xTag {
 41                 if tag == 0 {
 42                     startX = x
 43                 }
 44             }
 45             if let sx = startX {
 46                 var xSet:Set<Int> = [sx]
 47                 func yforxSet(_ xSet:Set<Int>) -> Set<Int> {
 48                     var ySet:Set<Int> = []
 49                     for x in xSet {
 50                         for point in xPointsMap[x] ?? [] {
 51                             let y = point[1]
 52                             if yTag[y] == 0 {
 53                                 ySet.insert(y)
 54                             }
 55                         }
 56                     }
 57                     return ySet
 58                 }
 59                 
 60                 func xforySet(_ ySet:Set<Int>) -> Set<Int> {
 61                     var xSet:Set<Int> = []
 62                     for y in ySet {
 63                         for point in yPointsMap[y] ?? [] {
 64                             let x = point[0]
 65                             if xTag[x] == 0 {
 66                                 xSet.insert(x)
 67                             }
 68                         }
 69                     }
 70                     return xSet
 71                 }
 72                 var ySet = yforxSet(xSet)
 73                 var deltaY:Set<Int> = ySet
 74                 
 75                 while true {
 76                     var thisX = xforySet(deltaY)
 77                     var deltaX = thisX.subtracting(xSet)
 78                     if (deltaX.count == 0) {
 79                         break;
 80                     }
 81                     xSet = xSet.union(deltaX)
 82                     var thisY = yforxSet(deltaX)
 83                     deltaY = thisY.subtracting(ySet)
 84                     ySet = ySet.union(deltaY)
 85                 }
 86                 
 87                 var pointsCount = 0
 88                 
 89                 for x in xSet {
 90                     xTag[x] = currentTag
 91                     pointsCount += xPointsMap[x]?.count ?? 0
 92                 }
 93                 for y in ySet {
 94                     yTag[y] = currentTag
 95                 }
 96                 
 97                 if (pointsCount >= 1) {
 98                     totalMove += pointsCount - 1
 99                 }
100                 
101                 currentTag += 1
102             } else {
103                 break
104             }
105             
106         }
107         return totalMove;
108     }
109 }

1956ms

 1 class Solution {
 2     func removeStones(_ stones: [[Int]]) -> Int {
 3         var sets = [(Set<Int>, Set<Int>)]()
 4         for i in 0..<stones.count {
 5             let s = stones[i]
 6             let row = sets.index(where: { $0.0.contains(s[0]) })
 7             let col = sets.index(where: { $0.1.contains(s[1]) })
 8             if let col = col, let row = row, col != row {
 9                 let unionRows = sets[row].0.union(sets[col].0)
10                 let unionCols = sets[row].1.union(sets[col].1)
11                 if row < col {
12                     sets.remove(at: col)
13                     sets.remove(at: row)
14                 }else {
15                     sets.remove(at: row)
16                     sets.remove(at: col)
17                 }
18                 sets.append((unionRows, unionCols))
19             } else if let row = row {
20                 sets[row].0.insert(s[0])
21                 sets[row].1.insert(s[1])
22             } else if let col = col {
23                 sets[col].0.insert(s[0])
24                 sets[col].1.insert(s[1])
25             } else {
26                 sets.append((Set([s[0]]), Set([s[1]])))
27             }
28         }
29         return stones.count-sets.count
30     }
31 }

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原文地址：https://www.cnblogs.com/strengthen/p/10015292.html