c++ - BFS Segmentation Fault -

#include <iostream> #include <sstream> #include <fstream> #include <cstdlib> #include <list> // #include "bst.h"  using namespace std;  class graph {   int v; // number of vertices   list<int> *adj; // pointer array of adjacency list  public:   graph(int v); // constructor   void addedge(int v, int w); // function add edge graph   void bfs(int s); // prints breadth first search graph s. };  //defining constructor graph::graph(int v) {   this->v = v;   adj = new list<int>[v]; }   // function add edges vertice. void graph::addedge(int v, int w) {   adj[v].push_back(w); // adding w v's list }   // function print out breadth first search given graph starting @ s. void graph::bfs(int s) {   bool *visited = new bool[v];    cout << "value of v: " << v << endl;   for(int = 0; < v; i++)     visited[i] = false;    // create queue bfs   list<int> queue;    //marking starting node visited , adding queue.   visited[s] = true;   queue.push_back(s);    // iterator iterate on adjacent list vertices   list<int>::iterator i;    while(!queue.empty())   {      // printing current vertex , removing queue     s = queue.front();     cout << s << " ";     queue.pop_front();       // going through adjacency list , adding queue if has not been visited.       (i = adj[s].begin(); != adj[s].end(); i++)       {         if(!visited[*i] )         {           visited[*i] = true;           queue.push_back(*i);         }       }   } }    int main(int argc, char* argv[]) {   // if user didn't provide filename command line argument,   // print error , exit.   if (argc != 3)   {       cout << "usage: " << argv[0] << " <filename>  <starting node index>" << endl;       exit(1);   }    string line;   int size;   int starting_vertice;   char colon;   int vertex;   ifstream myfile (argv[1]);   if (myfile.is_open())   {     getline(myfile, line);     istringstream iss(line);     iss >> size;      // initializing graph of size taken in.     graph g(size);      cout << "vertex: " << "connected vertices" << endl;     (int = 0; < size; i++)     {       getline(myfile, line);       istringstream iss(line);       iss >> starting_vertice;       iss >> colon;        while (iss >> vertex)       {         g.addedge(starting_vertice, vertex);       }       cout << endl;     }      myfile.close();      cout << "breadth first search starting @ vertex " << argv[2] << " : " << endl;     // cout << atoi(argv[2]) << endl;     g.bfs( atoi(argv[2]) );   }    else     cout << "unable open file" << endl;    return 0;  } 

this code implement breadth first search specific input file. input file follows:

4 1:2 3 4 2:4 3:4 4: 

i know i'm getting segmentation fault while looping through adjacency list last vertex can't, life of me, figure out how fix this. help?

edit: also, starting node index gave 1.

welcome off-by-one club. arrays zero-indexed. in graph, create list of size v , then, through graph::addedge, go on access v-th element of v-sized array adj. fix this, have 2 choices - number vertices 0 v-1, or increase size of adj v+1. latter:

graph::graph(int v) {   this->v = v;   adj = new list<int>[v+1];                      vvvvvv  }