dfs added

Author: piyush140800

dfs.cpp

@@ -0,0 +1,140 @@
+#include <iostream>
+#include <limits.h>
+using namespace std;
+#define black 0
+#define grey 1
+#define white 2
+struct adjlistnode
+{
+	int data;
+	struct adjlistnode *next;
+};
+struct adjlist
+{
+	struct adjlistnode *head;
+};
+struct graph
+{
+	int vertices;
+	struct adjlist* array;
+	int *color;
+};
+struct adjlistnode* c_node(int v)
+{
+	struct adjlistnode* node=new struct adjlistnode;
+	node->data=v;
+	node->next=NULL;
+	return node;
+}
+struct graph* creategraph(int numv)
+{
+	struct graph* g= new graph;
+	g->vertices=numv;
+	g->array=new struct adjlist[(numv)*sizeof(adjlist)];
+	g->color=new int[numv*sizeof(int)];
+	for(int i=0;i<numv;i++)
+	{
+		g->array[i].head=NULL;
+		g->color[i]=white;
+	}
+	return g;
+}
+void addedge(struct graph* g,int v1,int v2)
+{
+	 struct adjlistnode* temp=c_node(v1);
+	 temp->next=g->array[v2].head;
+	 g->array[v2].head=temp;
+	 temp=c_node(v2);
+	 temp->next=g->array[v1].head;
+	 g->array[v1].head=temp;
+}
+void print(struct graph* g,int v)
+{
+	int i;
+	for(i=1;i<=v;i++)
+	{
+		struct adjlistnode *q=(struct adjlistnode*)malloc(sizeof(struct adjlistnode));
+		q=g->array[i].head;
+		cout<<"for node"<<i<<endl;
+		while(q)
+		{
+			cout<<q->data;
+			q=q->next;
+		}
+		cout<<endl;
+	}
+}
+struct stack
+{
+	int top;
+	int len;
+	int *array;
+};
+struct stack* createstack(int numv)
+{
+	struct stack* s=new struct stack;
+	s->top=-1;
+	s->len=numv;
+	s->array = new int[numv*sizeof(int)]; 
+	return s;
+}
+int isEmpty(struct stack* stack) //checks if the stack is empty
+{ 
+    return stack->top == -1; 
+} 
+int pop(struct stack* stack) //pops and removes the top element
+{ 
+    if (isEmpty(stack)) 
+        return INT_MIN; 
+    return stack->array[stack->top--]; 
+} 
+int peek(struct stack* stack) /* fucntion returns the top without removing it*/
+{ 
+    if (isEmpty(stack)) 
+        return INT_MIN; 
+    return stack->array[stack->top]; 
+} 
+void push(struct stack* stack, int item) // pushes the item at the top
+{ 
+    stack->array[++stack->top] = item; 
+} 
+void dfs(struct graph* g,int startvertex,struct stack* s)
+{
+	push(s,startvertex);
+	g->color[startvertex]=grey;
+	while(!isEmpty(s))
+	{
+		int u=peek(s);
+		struct adjlistnode* v=g->array[u].head;
+		while(v)
+		{
+			if(g->color[v->data]==white)
+				dfs(g,v->data,s);
+			else if(g->color[v->data]==grey && v->data!=u)
+			{
+				pop(s);
+				g->color[u]=black;
+				cout<<"cycle detected"<<endl;
+				return;
+			}
+			v=v->next;
+		}
+		pop(s);
+	}
+}
+int main()
+{
+	struct graph* graph = creategraph(7);
+	struct stack* s=createstack(7);
+    addedge(graph, 1, 2);
+    addedge(graph, 1, 5);
+    addedge(graph, 2, 3);
+    addedge(graph, 2, 6);
+    addedge(graph, 3, 7);
+    addedge(graph, 3, 4);
+    addedge(graph, 5, 6);
+    addedge(graph, 6, 7);
+    print(graph,7);
+ 	dfs(graph, 1,s);
+
+}