Thread: Palindrome Algorithm in C .

Hello to all. I have some confusion here.....

My code :

Code:

#include<stdio.h>
#include<string.h>
#include<stdbool.h>
#include <ctype.h>
#define STR_LEN 50
int is_palindrome( const char []);
void read_line(char [] , int );
int main( void )
{
    char str[STR_LEN + 1] = {'\0'};
    
    for(;;) {
    
    printf("\n Enter a word (Enter a single letter to terminate) : \n");
    read_line(str , STR_LEN );  
    
    if(strlen(str) < 2)
    break;
    
    if( is_palindrome( str ) )
    printf(" Word %s is  palindrome " , str);
    
    else
    printf(" Word %s is not palindrome " , str);
}
        
        return 0;
}
void read_line(char str[] , int n)
{
    int ch , i=0;
    while( (ch = getchar()) != '\n' ) {
        
        if( !isalpha(ch)) {
        printf(" \n *Rejected* '%c' is not a letter " , ch);
        continue;
	    }    
        
        if(i < n )
        str[i++] = ch;
    }
        
        str[i] = '\0';
}

int is_palindrome(const char* str) {
	
    const char* last = str + strlen(str) - 1; 
    while (str < last) {
        if (*str++ != *last--) return 0;
    }             
 
    return 1;
}

I have a basic question not about the code but about the algorithm which code uses in order to find a palindrome.

How many pass algorithm does? 1 + 1/2 or 2?