added DFS finding bridges

Graph/DFS (Depth First Search).cpp

@@ -0,0 +1,49 @@
+#include <bits/stdc++.h>
+#define lli long long int
+#define endl "\n"
+using namespace std;
+
+bool visited[105];		//by default it is initialised with false;
+vector <int> v1[105];
+
+
+void DFS(int vertex)
+{
+	if(visited[vertex] == false)
+	{
+		cout<<vertex<<" ";
+		visited[vertex] = true;
+		for(int j = 0; j < v1[vertex].size(); j++)
+		{
+			DFS(v1[vertex][j]);
+		}
+	}
+	return;
+}
+
+int main()
+{
+	int no_of_vertex, no_of_edges;
+	cout<<"Enter the number of vertices: ";
+	cin>>no_of_vertex;
+
+
+	memset(visited, false, sizeof(visited));
+
+	int i, j;
+	cout<<"Enter the number of edges: ";
+	cin>>no_of_edges;
+
+	for(int edge = 1; edge <= no_of_edges; edge++)
+	{
+		cout<<"Enter the vertices for edge "<<edge<<": ";
+		cin>>i>>j;
+		v1[i].push_back(j);
+		v1[j].push_back(i);
+	}
+
+	cout<<"DFS: ";
+	for(i = 1; i <= no_of_vertex; i++)
+		DFS(i);
+	return 0;
+}

Graph/Finding Bridges.cpp

@@ -0,0 +1,57 @@
+#include <bits/stdc++.h>
+#define lli long long int
+#define endl "\n"
+#define MAX 105
+using namespace std;
+
+
+vector <int> v1[MAX];
+vector <bool> visited(MAX, false);
+vector <int> in(MAX, 0);
+vector <int> low(MAX, 0);
+int timer;
+
+void DFS(int i, int par)
+{
+	visited[i] = true;
+	in[i] = timer;
+	low[i] = timer;
+	timer++;
+	for(int j =0; j<v1[i].size(); j++)
+	{
+		if(v1[i][j] == par)
+		{
+			//that means its his parent, so its not the back edge
+			continue;
+		}
+		if(visited[v1[i][j]] == true)
+		{
+			//its a backedge
+			low[i] = min(low[i], in[v1[i][j]]);
+		}
+		else
+		{
+			//forward edge...we will call dfs
+			DFS(v1[i][j], i);
+			if(low[v1[i][j]] > in[i])
+				cout<<"Found a bridge: "<<i<<" -> "<<v1[i][j]<<endl;
+			low[i] = min(low[i], low[v1[i][j]]);
+		}
+	}
+}
+
+int main()
+{
+	int v, e, x, y;
+	cin>>v>>e;
+	timer = 0;
+	for(int i = 0; i<e; i++)
+	{
+		cin>>x>>y;
+		v1[x].push_back(y);
+		v1[y].push_back(x);
+	}
+
+	DFS(1,-1);
+
+}

Graph/In Out Time of Nodes.cpp

@@ -0,0 +1,48 @@
+#include <bits/stdc++.h>
+#define lli long long int
+#define endl "\n"
+using namespace std;
+
+bool visited[105];
+vector <int> v1[105];
+vector <int> timein(105, 0);
+vector <int> timeout(105, 0);
+int counter;
+
+void dfs(int i)
+{
+	visited[i] = true;
+	timein[i] = ++counter;
+	for(int j = 0; j<v1[i].size(); j++)
+	{
+		if(visited[v1[i][j]] == false)
+			dfs(v1[i][j]);
+	}
+	timeout[i] = ++counter;
+}
+
+int main()
+{
+	counter = 0;
+	int v, e, x, y;
+	cout<<"Enter the number of vertices and edges: ";
+	cin>>v>>e;
+	for(int  i = 0 ; i<e; i++)
+	{
+		cin>>x>>y;
+		v1[x].push_back(y);
+		v1[y].push_back(x);
+	}
+
+
+	dfs(1);
+
+	for(int i = 1; i<=v; i++)
+		cout<<timein[i]<<" ";
+	cout<<endl;
+
+	for(int i = 1; i<=v; i++)
+		cout<<timeout[i]<<" ";
+	cout<<endl;
+
+}

Graph/Subtree size using DFS.cpp

@@ -0,0 +1,43 @@
+#include <bits/stdc++.h>
+#define lli long long int
+#define endl "\n"
+#define MAX 105
+using namespace std;
+
+vector <int> v1[MAX];
+vector <int> subSize(MAX, 0);
+vector <bool> visited(MAX, false);
+
+int DFS(int i)
+{
+	visited[i] = true;
+	int count = 1;
+	for(int j = 0; j<v1[i].size(); j++)
+	{
+		if(visited[v1[i][j]] == false)
+		{
+			count += DFS(v1[i][j]);
+		}
+	}
+	subSize[i] = count;
+	return subSize[i];
+}
+
+
+int main()
+{
+	int v, e, x, y;
+	cout<<"Enter the number of vertices and edges: ";
+	cin>>v>>e;
+	for(int i =0 ; i<e; i++)
+	{
+		cin>>x>>y;
+		v1[x].push_back(y);
+		v1[y].push_back(x);
+	}
+
+	int ans = DFS(1);
+
+	for(int i = 1; i<=v; i++)
+		cout<<i<<": "<<subSize[i]<<endl;
+}