# C++ > Data Structures Code Examples

## Graphs program

``` Graphs program #include <iostream.h> #include <conio.h> class graph { private:int n; int **a; int *reach; int *pos; public:graph(int k=10); void create(); void dfs(); void dfs(int v,int label); int begin(int v); int nextvert(int v); }; void graph::graph(int k) { n=k; a=new int *[n+1]; reach=new int[n+1]; pos=new int [n+1]; for(int i=1;i<=n;i++) pos[i]=0; for(int j=1;j<=n;j++) a[j]=new int[n+1]; } void graph::create() { for(int i=1;i<=n;i++) { cout<<"Enter the "<<i<<"th row of matrix a: "; for(int j=1;j<=n;j++) cin>>a[i][j]; } for(int k=1;k<=n;k++) reach[k]=0; } void graph::dfs() { int label=0; for(int i=1;i<=n;i++) if(!reach[i]) { label++; dfs(i,label); } cout<<" The contents of the reach array is: ; for(int j=1;j<=n;j++) cout<<reach[j]<<" "; } void graph::dfs(int v,int label) { cout<<v<<" "; reach[v]=label; int u=begin(v); while(u) { if(!reach[u]) dfs(u,label); u=nextvert(v); } } int graph::begin(int v) { if((v<1)&&(v>n)) cout<<"Bad input "; else for(int i=1;i<=n;i++) if(a[v][i]==1) { pos[v]=i; return i; } return 0; } int graph::nextvert(int v) { if((v<1)&&(v>n)) cout<<"Bad input "; else for(int i=pos[v]+1;i<=n;i++) if(a[v][i]==1) { pos[v]=i; return i; } return 0; } void main() { clrscr(); int x; cout<<"Enter the no of vertices: "; cin>>x; graph g(x); g.create(); cout<<"dfs is....."; g.dfs(); getch(); } ```