Segmentation fault in c++ program for dijkstra's algorithm

This is my code.. I tried hard to detect the fault but it compiles properly and then gives segmentation fault while executing...

#include<iostream>
#include<string>
using namespace std;

#define infinity 999
#define MAX 10

int min(int dis[],bool vis[],int n);
void print_dij(int dis[],int n);

class graph
{
    int g[MAX][MAX];
    public:
        int n;
        graph()
        {
            n=0;
        }
        void readgraph();
        void printgraph();
        void dij();
};
void graph::readgraph()
{
    int i,j;
    cout<<"\nEnter the no of vertices::";
    cin>>n;
    cout<<"\nEnter the adjacency matrix::";
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            cout<<"\n["<<i<<"]["<<j<<"]::";
            cin>>g[i][j];
        }
    }
}
void graph::printgraph()
{
    int i,j;
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
            cout<<g[i][j];
        cout<<"\n";
    }
}
void graph::dij()
{
    int dis[20],i,j,start,u;
    bool vis[20];
    cout<<"\nEnter the index number of starting node::";
    cin>>start;
    for(i=0;i<n;i++)
        for(j=0;j<n;j++)
            if(g[i][j]==0)
                g[i][j]=infinity;

    for(i=0;i<n;i++)        //Initialising the arrays dis[] and vis[]
    {
        dis[i]=infinity;
        vis[i]=false;
    }
    dis[start]=0;
    for(i=0;i<n-1;i++)         //Finding the shortest path
    {
        u=min(dis,vis,n);
        vis[u]=true;
        for(j=0;j<n;j++)
            if(!vis[j] && g[u][j] && dis[u]!=infinity && dis[u]+g[u][j]<dis[j])
                dis[i]=dis[u]+g[u][j];
    }
    cout<<"\nThe shortest path is::->>>>>\n";
    print_dij(dis,n);
}
int min(int dis[],bool vis[],int n)      //To find the vertex with min distance from the source
{
    int index,i,min=infinity;
    for(i=0;i<n;i++)
        if(vis[i]=false && dis[i]<=min)
        {
            min=dis[i];
            index=i;
        }
    return index;
}
void print_dij(int dis[],int n)       //To print the shortest path
{
    int i;
    cout<<"\nVertices\tMinimum distance";
    for(i=0;i<n;i++)
    {
        cout<<"\n"<<i<<"\t"<<dis[i];
    }
}       
int main()
{
    graph g;
    int start;
    g.readgraph();
    cout<<"\nThe entered graph is::\n";
    g.printgraph();
    g.dij();
    return 0;
}

It seems like the fault is in the loop for finding the shortest path in the dij() function. But still i am not able to figure out the problem. Please help me out... :-|

Upvotes: 0