a Unhandled exception :Access violation reading location 0x00000004

I get this error in the debugging mode when i first encounter the marked line in the code below

#include<fstream>
#include<iostream>
#include<math.h>
#include<string>

using namespace std;

int main()
{int t,i,j,k,n,g[100],w[100],opp[100];
float rpi[100],wp[100],owp[100],oowp[100];
char s[100][100];
ifstream ip; ip.open("A-small-practice.in"); ofstream op; op.open("A_out.in");
ip>>t; 
for(i=0;i<t;i++)
  { ip>>n;
    memset(g,0,sizeof(g));
    memset(w,0,sizeof(w));
    memset(op,0,sizeof(op));
    memset(rpi,0,sizeof(rpi));
    memset(wp,0,sizeof(wp)); 
    memset(owp,0,sizeof(owp));
    memset(oowp,0,sizeof(oowp));
    memset(s,'.',sizeof(s));

    for(j=0;j<n;j++)
      {for(k=0;k<n;k++)
        {ip>>s[j][k]; //<--------------------the error occurs here
        if(s[j][k]=='0')
          g[j]++;
    if(s[j][k]=='1')
      {g[j]++;w[j]++;}
        }
      wp[j]=w[j]/g[j];
     }

    for(j=0;j<n;j++)
      {for(k=0;k<n;k++)
       if(j!=k && s[k][j]!='.')
           {owp[j]+=(wp[k]*g[k]-s[k][j])/(g[k]-1);
           opp[j]++;
           }
       owp[j]/=opp[j];
      } 

    for(j=0;j<n;j++)
    开发者_如何学编程  {for(k=0;k<n;k++)
        {if(j!=k && s[k][j]!='.')
         oowp[j]+=owp[k];
        }
       oowp[j]/=opp[j]; 
      }

   op<<"Case #"<<i+1<<": \n"; 
    for(j=0;j<n;j++)
    {rpi[j]=(0.25*wp[j]) + (0.5*owp[j]) +(0.25*oowp[j]);
    op<<rpi[j]<<"\n";
     } 
 } 
return 0; 
}

the debugger breaks at this code segment when stepped in. The loops and logic the value size is all correct i don't know where the overflow is ocurring..is there any other cause for this?

    class _Sentry_base
    {   // stores thread lock and reference to input stream
public:
    __CLR_OR_THIS_CALL _Sentry_base(_Myt& _Istr)
        : _Myistr(_Istr)
        {   // lock the stream buffer, if there
        if (_Myistr.rdbuf() != 0)//<-------------break points here
            _Myistr.rdbuf()->_Lock();
        }

You don't need to use memset for the 1D arrays. For example

 int g[100] = {0};

will work.

For the 2D array, loop through using a for loop and set each element to '.', or stick with the memset for that step.

In terms of your actual problem, you may need to use ip.get() to read character by character instead.