c programming finds the two digit number that was repeated most - c

Question

I have this code that the input is random for example :
33 32 65 55 44 pe *&44^ %123^
now I need to find which two digit number was repeaed most (and the number needs to contain digits from 1 to 9, which mean 10,30.. are not valid numbers), now what seperate between two digit number to another is every input exept for another number,
in this case I want the output to be 44 then I will print:
The winner couple is: 4 blue, 4 red.
now I thought the best way to do something like this is using 2D array, that when a input is valid I will apdate the array in the sutble place, and after that I will find the maximum place in the array.
here is my code so far :
#include <stdio.h>
#include <stdlib.h>
#define N 9
int is_digit(char c);
void update_array(int num[N][N]);
int find_max(int b[N][N]);
int main()
{
int i,j;
int num[N][N];
int maximum=0,a=0,b=0;
for(i=0;i<N;++i)
{
for(j=0;j<N;++j)
{
num[i][j]=0;
}
}
update_array(num);
maximum=find_max(num);
a=maximum/10;
b=maximum%10;
printf("The winner couple is: %d blue, 4%d red.",a,b);
return 0;
}
int is_digit(char c)
{
if(c<'0'&&c>'9')
return 1;
else
return 0;
}
void update_array(int num[N][N])
{
char c;
int digit = 0;
int digits = 0;
int redIndex = 0;
int blueIndex = 0;
while (scanf("%c", &c) != EOF)
{
if (is_digit(c))
{
digits++;
digit = c -'0';
if (digits == 1)
redIndex = digit;
else if (digits == 2)
blueIndex = digit;
}
else
{
if (digits == 2)
{
(num[redIndex][blueIndex]++);
}
digits = 0;
}
}
int find_max(int b[N][N])
{
int max = b[0][0];
int x,y;
for (x = 0; x < N; x++)
{
for (y = 0; y < N; y++)
{
if (max < b[x][y])
{
max = b[x][y];
}
}
}
}
return max;
}
the code gives me incorect output , i chicked all of the functions and they are good ,exept for update_array function i think there is something icorrect, basicly this function chicks where there is two digit number and update the suatble place in array, so i can then use fin_max function and find the maximum..
plz anyhelp of why it gives me incorect values, i know i should use debugg but i never knew about this untill now and i don't have the time to learn this now and use it cause i need to submit this in a couple of hours !

Answer 1

In your code you do if (isdigit(c)), but isdigit is a different (standard library) function! You have to #include <ctype.h> to use it.

Answer 2

Using continue; outside loop is illegal.
You didn't declare nor define w.
A semicolon is missing after what seems calling of function w.
Try this because is_digit is not used:
void is_digit(char c)
{
(void)c; /* avoid warning for unused variable */
}
Note that this is invaiid because the return type is void:
void is_digit(char c)
{
return (c>'0'&&c<='9');
}
Don't forget to add #include <ctype.h> to use isdigit().
Also, replace
if (isdigit(c))
with
if (isdigit((unsigned char)c) && c != '0')
to avoid undefined behavior for passing out-of-range value and reject digit 0.

Answer 3

You've declared the function with the name is_digit() and later you are using it with the name isdigit().
So, after changing the above mentioned error, your code would look like
#include <stdio.h>
#include <stdlib.h>
#define N 9
int is_digit(char c);
void update_array(int num[N][N]);
int find_max(int b[N][N]);
int main()
{
int i,j;
int num[N][N];
int maximum=0,a=0,b=0;
for(i=0;i<N;++i)
{
for(j=0;j<N;++j)
{
num[i][j]=0;
}
}
update_array(num);
maximum=find_max(num);
a=maximum/10;
b=maximum%10;
printf("The winner couple is: %d blue, 4%d red.",a,b);
return 0;
}
int is_digit(char c)
{
if(c<'0'&&c>'9')
return 1;
else if(c>'0'&&c<='9')
return 0;
}
void update_array(int num[N][N])
{
char c;
int digit = 0;
int digits = 0;
int redIndex = 0;
int blueIndex = 0;
while (scanf("%c", &c) != EOF)
{ // <= while started
if (is_digit(c))
{ // <= if started
digits++;
digit = c -'0';
if (digits == 1)
redIndex = digit;
else if (digits == 2)
blueIndex = digit;
} // <= If ended
else
{ // <= else started
if (digits == 2)
{
(num[redIndex][blueIndex]++);
}
digits = 0;
} // <= else ended
} // <= while ended
//where is the function ending?
} //hence another curly braces needed.
int find_max(int b[N][N])
{
int max = b[0][0];
int x,y;
for (x = 0; x < N; x++)
{
for (y = 0; y < N; y++)
{
if (max < b[x][y])
{
max = b[x][y];
}
}
}
return max;
}