A Algorithm Implementation for Longest Palindrome Substring Issue

A Algorithm Implementation for Longest Palindrome Substring Issue

Here is my simple recursive implementation for this issue.
Without full test.
If any bug, please let me know. thank you so much.

Anybody could show me a non-recursive right implementation for this question?
On internet, many implementation can not pass my simple test.
And I spent much time on this issue and no good resolution gained even now.
So, I hope you can write a nice non-recursive one and post on this page. thank you again.

the best from Jonsen.

#include  < stdio.h >
#include  < string .h >
static   int  len  =   0 ;
static   char *  str  =  NULL;

/* *
 * find all possible palindromes starting with str[m]
  */
int  scan( int  m,  int  n){
     if (m  >  n)  return   0 ;
     int  i  =  m, j  =  n;
     while (i  <  j){
         if (str[i]  ==  str[j]) { i ++ ; j -- ; }
         else   break ;
    }
     if (i  >=  j)  return  n - m + 1 ;
     else   return  scan(m, n - 1 );
}

/* *
 * process str starting with m and ending with n.
 * then, process str starting with m+1, and ending with n.
 * if length of string is smaller than len gained, there is
 * no need to process the str anymore and avoiding useless 
 * processing.
  */
void  process( int  m,  int  n){
    printf( " process(%d, %d)\n " , m, n);
     if (m  >  n)  return ;
     int  tmp  =  scan(m, n);
    printf( " scan(%d, %d) and rtv = %d\n " , m, n, tmp);
    len  =  tmp  >  len  ?  tmp : len;
     if (n - m  >  len) process(m + 1 , n);
}

int  main( int  argc,  char *  argv[]){
    str  =  argv[ 1 ];
    process( 0 , strlen(str)  -   1 );
    printf( " len = %d\n " , len);
     return   0 ;
}

Running log:

[root@localhost tmp]# gcc longest_palindrome_substring.c  &&  time a. out  abcabcddcbbcddcba
process( 0 ,  16 )
scan( 0 ,  16 ) and rtv  =   1
process( 1 ,  16 )
scan( 1 ,  16 ) and rtv  =   1
process( 2 ,  16 )
scan( 2 ,  16 ) and rtv  =   1
process( 3 ,  16 )
scan( 3 ,  16 ) and rtv  =   14
len  =   14

real    0m0.001s
user    0m0.000s
sys     0m0.001s
[root@localhost tmp]#