solve

Author: sonjh1217

number-of-connected-components-in-an-undirected-graph/sonjh1217.swift

@@ -0,0 +1,41 @@
+class Solution {
+    // O(n+m) (m = edges.count) time / O(n+m) space
+    func countComponents(_ n: Int, _ edges: [[Int]]) -> Int {
+        var graph = [[Int]](repeating: [], count: n)
+        for edge in edges {
+            graph[edge[0]].append(edge[1])
+            graph[edge[1]].append(edge[0])
+        }
+        
+        var visited = [Bool](repeating: false, count: n)
+        var connectedComponents = 0
+        
+        for i in 0..<n {
+            if visited[i] {
+                continue
+            }
+            var queue = [Int]()
+            queue.append(i)
+            visited[i] = true
+            var head = 0
+                        
+            while queue.count > head {
+                let current = queue[head]
+                head += 1
+                
+                for node in graph[current] {
+                    if !visited[node] {
+                        visited[node] = true
+                        queue.append(node)
+                    }
+                }
+            }
+            connectedComponents += 1
+        }
+        
+        return connectedComponents
+    }
+}
+
+print(Solution().countComponents(3, [[0,1], [0,2]]))
+print(Solution().countComponents(6, [[0,1], [1,2], [2, 3], [4, 5]]  ))