Roman numbers to decimal numbers, getting garbage value - c++

Question

I have to create a program for converting Roman numerals to decimal numbers for which I'm getting garbage value as an output.
The fact is I have double checked my logic and it seems to be correct.
How can I correct it?
Here's my code:
#include<iostream>
#include<cstring>
using namespace std;
class RomanType
{
char str[10];
int d;
public:
void accept()
{
cout<<"Enter Roman No. in capitals:"<<endl;
cin>>str;
convert(str);
}
void convert(char str1[10])
{
int j=0;
for(j=0;j<strlen(str1);j++)
{
if( str1[j]=='I')
{
if(str1[j+1]=='V' || str1[j+1]=='X')
{
d=d-1;
cout<<j<<endl;
}
else
{
d=d+1;
cout<<d<<endl;
}
}
if ( str1[j]=='V')
d=d+5;
if(str1[j]=='X')
{
if(str1[j+1]=='L' || str1[j+1]=='C')
d=d-10;
else
d=d+10;
}
if(str1[j]=='L')
d=d+50;
if( str1[j]=='C')
{
if(str1[j+1]=='D' || str1[j+1]=='M')
d=d-100;
else
d=d+100;
}
if(str1[j]=='D')
d=d+500;
if(str1[j]=='M')
d=d+1000;
}
}
void display()
{
cout<<"It's decimal equivalent is="<<d<<endl;
}
};
main()
{
RomanType obj;
obj.accept();
obj.display();
}

Answer 1

Few points:
Don't directly jump to parsing high value romans. Start with I, V, and X only (i.e. target 1 to 10 first, then 11 to 20, then 21 to 39, 40 to 99, 100 to 499 etc.)
Don't assume that if I is given, it is given before or after V or X. It may be given for itself (eg. II - you else part assumes something).
Assign value of d with zero
Do step debugging, watch value of d and other variables. If debugger isn't good or available, do output the values on each step/iteration.
[Add] You need not to pass str to function convert, since they belong to same class, and convert can/would read the same content.

Answer 2

You didn't initialize d to 0
in convert put d=0 at the start

Answer 3

You didn't initialize d to 0. Please add this at the top of your convert function:
void convert(char str1[10])
{
int j=0;
d = 0;
. . .

Answer 4

OK guys thanks for the help. It's solved now. I had done a blunder and that was initialised d again in convert(), so that had made it as a local variable. See the comments:
#include<iostream>
#include<cstring>
using namespace std;
class RomanType
{
char str[10];
int d;
public:
void accept() // UNNECESSARILY NOT PASSING ANY STRING
{
cout<<"Enter Roman No. in capitals:"<<endl;
cin>>str;
convert();
}
void convert()
{
d=0;// PREVIOUSLY WRIITEN int d=0; so that was the mistake. Yay! it's solved :D
for(int j=0;j<10;j++)
{
if( str[j]=='I')
{
if(str[j+1]=='V' || str[j+1]=='X')
{
d=d-1;
// cout<<d<<endl;
}
else
{
d=d+1;
//cout<<d<<endl;
}
}
else if ( str[j]=='V')
d=d+5;
else if(str[j]=='X')
{
if(str[j+1]=='L' || str[j+1]=='C')
d=d-10;
else
d=d+10;
}
else if(str[j]=='L')
d=d+50;
else if( str[j]=='C')
{
if(str[j+1]=='D' || str[j+1]=='M')
d=d-100;
else
d=d+100;
}
else if(str[j]=='D')
d=d+500;
else if(str[j]=='M')
d=d+1000;
}
}
void display()
{
cout<<"It's decimal equivalent is="<<d<<endl;
}
};
main()
{
RomanType obj;
obj.accept();
obj.display();
}