Merge pull request #45 from dogra25130/graph-traversal

BFS / DFS traversals

graph/BFS/BFS.swift

@@ -0,0 +1,75 @@
+// MARK: - Basic requirement
+struct Edge {
+    let from: Int
+    let to: Int
+}
+
+public class Node {
+    var val: Int
+    var neighbors: [Int]
+    public init(_ val: Int) {
+        self.val = val
+        self.neighbors = []
+    }
+}
+
+// MARK: - BFS implementation
+func testBFS(edges: [Edge]) {
+
+    var graph = [Int: Node]()
+    for edge in edges {
+        graph[edge.from] = Node(edge.from)
+        graph[edge.to] = Node(edge.to)
+    }
+    for edge in edges {
+        graph[edge.from]?.neighbors.append(edge.to)
+        graph[edge.to]?.neighbors.append(edge.from)
+    }
+    var visited: [Bool] = Array(repeating: false, count: graph.count + 1)
+    var nodesOfCurrentLevel: [Int] = []
+
+    for node in 1...graph.count {
+        if visited[node] == false {
+            nodesOfCurrentLevel.append(node)
+            while(nodesOfCurrentLevel.isEmpty == false) {
+                var nodesOfNextLevel: [Int] = []
+                let sizeOfQueue = nodesOfCurrentLevel.count
+                for index in 0..<sizeOfQueue {
+                    let currNode = nodesOfCurrentLevel[index]
+                    if(visited[currNode] == true){
+                        continue
+                    }
+                    print("\(currNode) ")
+                    visited[currNode] = true
+                    guard let neighbors = graph[currNode]?.neighbors else { continue }
+                    for neigh in neighbors {
+                        if visited[neigh] == false {
+                            nodesOfNextLevel.append(neigh)
+                        }
+                    }
+                }
+                nodesOfCurrentLevel = nodesOfNextLevel
+            }
+        }
+    }
+}
+
+// MARK: - Input Graph
+func setup() {
+    let edges = [
+        Edge(from: 1, to: 2),
+        Edge(from: 1, to: 4),
+        Edge(from: 2, to: 3),
+        Edge(from: 2, to: 4),
+        Edge(from: 2, to: 5),
+        Edge(from: 3, to: 5),
+        Edge(from: 4, to: 5),
+        Edge(from: 4, to: 6),
+        Edge(from: 5, to: 6),
+        Edge(from: 5, to: 6),
+        Edge(from: 6, to: 7),
+    ]
+    testBFS(edges: edges)
+}
+
+setup()

graph/DFS/DFS.swift

@@ -0,0 +1,64 @@
+// MARK: - Basic requirement
+struct Edge {
+    let from: Int
+    let to: Int
+}
+
+public class Node {
+    var val: Int
+    var neighbors: [Int]
+    public init(_ val: Int) {
+        self.val = val
+        self.neighbors = []
+    }
+}
+
+// MARK: - DFS Recursion
+func dfs(vertex: Int, visited: inout [Bool], graph: [Int: Node]) {
+    if visited[vertex] == true {
+        return
+    }
+    visited[vertex] = true
+    print("\(vertex) ")
+    guard let neighbors = graph[vertex] else { return }
+    for neighbor in neighbors.neighbors {
+        dfs(vertex: neighbor, visited: &visited, graph: graph)
+    }
+}
+
+func testDFS(edges: [Edge]) {
+    var graph = [Int: Node]()
+    for edge in edges {
+        graph[edge.from] = Node(edge.from)
+        graph[edge.to] = Node(edge.to)
+    }
+    for edge in edges {
+        graph[edge.from]?.neighbors.append(edge.to)
+        graph[edge.to]?.neighbors.append(edge.from)
+    }
+    var visited: [Bool] = Array(repeating: false, count: graph.count + 1)
+    for node in 1...graph.count {
+        if visited[node] == false {
+            dfs(vertex: node, visited: &visited, graph: graph)
+        }
+    }
+}
+
+
+// MARK: - setup
+func setup() {
+    let edges = [
+        Edge(from: 1, to: 2),
+        Edge(from: 1, to: 4),
+        Edge(from: 2, to: 3),
+        Edge(from: 2, to: 4),
+        Edge(from: 2, to: 5),
+        Edge(from: 3, to: 5),
+        Edge(from: 4, to: 5),
+        Edge(from: 4, to: 6),
+        Edge(from: 5, to: 6),
+        Edge(from: 5, to: 6),
+        Edge(from: 6, to: 7),
+    ]
+    testDFS(edges: edges)
+}