DFS and BFS

Author: Ankitr19

Competitive Coding/Graphs/Graph_Search/BreadthFirstSearch/BFS.md

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+This is the algortihm for Breadth First Search in a given graph.
+
+-We take a starting vertex , and push all its adjacent vertexes in a queue.
+-Now we pop an element from a queue and push all its vertexes in the queue , and we also mark down these vertexes as visited.
+-After executing the code, we will get the vertex visited in a breadth first manner.

Competitive Coding/Graphs/Graph_Search/BreadthFirstSearch/Breadth_First_Search.cpp

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+#include<bits/stdc++.h>
+using namespace std;
+
+vector<bool>Visited;
+vector< vector<int> >Graph;
+
+void edge(int a,int b)
+{
+	Graph[a].push_back(b); //for directed
+
+	//If undirected graph is there, then add the following line
+	// Graph[b].push_back(a);
+}
+
+void BreadthFirstSearch(int u)
+{
+	queue<int>q;
+	q.push(u);
+	Visited[u]=true;
+
+	while(!q.empty())
+	{
+		int f=q.front();
+		q.pop();
+
+		cout<<f<<" ";
+		int ln=Graph[f].size();
+		for(int j=0;j<ln;j++)
+		{
+			if(!Visited[Graph[f][j]])
+			{
+				q.push(Graph[f][j]);
+				Visited[Graph[f][j]]=true;
+			}
+		}
+	}
+}
+
+int main()
+{
+	int n,e;
+	cin>>n>>e;
+	Visited.assign(n,false);
+	Graph.assign(n,vector<int>());
+
+	int a,b;
+	for(int i=0;i<e;i++)
+	{
+		cin>>a>>b;
+		edge(a,b);
+	}
+
+	for(int i=0;i<n;i++)
+	{
+		if(!Visited[i])
+		{
+			BreadthFirstSearch(i);
+		}
+	}
+	return 0;
+}

Competitive Coding/Graphs/Graph_Search/DepthFIrstSearch/DFS.md

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+This is the algortihm for Depth First Search in a given graph.
+
+-We take a starting vertex , and push all its adjacent vertexes in a stack.
+-Now we pop an element from a stack and push all its vertexes in the stack , and we also mark down these vertexes as visited.
+-After executing the code, we will get the vertex visited in a depth first manner.

Competitive Coding/Graphs/Graph_Search/DepthFIrstSearch/Depth_First_Search.cpp

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+#include<bits/stdc++.h>
+using namespace std;
+
+void addEdge(vector<int>adj[],int u,int v)
+{
+	//For undirected graph
+	adj[u].push_back(v);
+	adj[v].push_back(u);
+}
+
+void DFSUtil(int u,vector<int>adj[],vector<bool>&visited)
+{
+	visited[u]=true;
+	cout<<u<<" ";
+	for(int i=0;i<adj[u].size();i++)
+	{
+		if(visited[adj[u][i]]==false)
+			DFSUtil(adj[u][i],adj,visited);
+	}
+}
+
+void DFS(vector<int>adj[],int V)
+{
+	vector<bool>visited(V,false);
+	for(int u=0;u<V;u++)
+	{
+		if(visited[u]==false)
+		{
+			DFSUtil(u,adj,visited);
+		}
+	}
+}
+
+int main()
+{
+	 int V = 5;
+    vector<int> adj[V];
+    addEdge(adj, 0, 1);
+    addEdge(adj, 0, 4);
+    addEdge(adj, 1, 2);
+    addEdge(adj, 1, 3);
+    addEdge(adj, 1, 4);
+    addEdge(adj, 2, 3);
+    addEdge(adj, 3, 4);
+    DFS(adj, V);
+    cout<<"\n";
+    return 0;
+}