From d3a2320a5025b9e3df714c0d288e892b81e607fe Mon Sep 17 00:00:00 2001
From: Rukmini Meda <44504940+Rukmini-Meda@users.noreply.github.com>
Date: Fri, 27 Mar 2020 13:13:33 +0530
Subject: [PATCH] Breadth first search using dart (#2560)

---
 .../Breadth_First_Search.dart                 | 99 +++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 Breadth_First_Search/Breadth_First_Search.dart

diff --git a/Breadth_First_Search/Breadth_First_Search.dart b/Breadth_First_Search/Breadth_First_Search.dart
new file mode 100644
index 0000000000..895b1f5f30
--- /dev/null
+++ b/Breadth_First_Search/Breadth_First_Search.dart
@@ -0,0 +1,99 @@
+// Required library to use inbuilt queues in Dart
+import 'dart:collection';
+// Required library to use standard output facility of dart
+import 'dart:io';
+
+// Function to find the breadth first search of a graph
+void Breadth_First_Search( var graph, int source, int no_vertices ) {
+    // Queue to order nodes levelwise or breadthwise
+    var queue = Queue();
+    // A list to keep track of visited nodes
+    var visited = new List(no_vertices);
+    // Initializing the list
+    for(int i = 0; i < no_vertices; i++){
+        visited[i] = 0;
+    }
+    // Adding the source node to queue
+    queue.add(source);
+    // Marking the node visited
+    visited[source] = 1;
+    int val;
+
+    while(queue.isNotEmpty){
+        val = queue.removeFirst();
+        stdout.write("$val ");
+        
+        //Visiting neighbours of the dequed node  
+        for(int i = 0; i < no_vertices; i++){
+            if(graph[val][i] == 1 && visited[i] == 0){
+                queue.add(i);
+                visited[i] = 1;
+            }
+        }
+    } 
+}
+
+// Driver method of the program
+void main() {
+
+    // Reading from the standard input
+    print("Which graph do you want to enter ( directed/ undirected ):");
+    String mode = stdin.readLineSync().toString();
+
+    print("Enter number of vertices:");
+    var input = stdin.readLineSync();
+    int no_vertices = int.parse(input);
+    
+    // Graph is implemented as adjacency matrix.
+    var graph = new List.generate(no_vertices, (_) => new List(no_vertices));
+    for(int i = 0; i < no_vertices; i++){
+        for(int j = 0; j < no_vertices; j++){
+            graph[i][j] = 0;
+        }
+    }
+  
+    print("Enter number of edges:");
+    var input1 = stdin.readLineSync();
+    int no_edges = int.parse(input);
+    print("Enter source and destination vertices of edges:\n");
+    print("Note: Enter source and destination vertices as 0,1,2,...");
+    
+    for(int i = 1; i <= no_edges; i++){
+      
+        print("Edge #$i:");
+        
+        print("Enter source vertex:");
+        int source = int.parse(stdin.readLineSync());
+
+        print("Enter destination vertex:");
+        int destination = int.parse(stdin.readLineSync());
+
+        if(mode == "undirected"){
+            graph[source][destination] = 1;
+            graph[destination][source] = 1;
+        }
+        else {
+            graph[source][destination] = 1;
+        }
+
+    }
+
+    print("Enter the source vertex from which BFS should begin:");
+    int source1 = int.parse(stdin.readLineSync());
+
+    // Sample input graph
+    // 0 - 1 - 2
+    // |     /
+    // 3 - 4
+
+    print("Vertices in Breadth First Search of the graph in sample input is: ");
+
+    // Breadth First Search of the above graph
+    Breadth_First_Search(graph,source1,no_vertices);
+
+    // Sample Output
+    // 0 1 3 2 4
+
+}
+
+