Programming Classics: Implementing the World's Best Algorithms by Oliver. Smilar text implementation.

smilar.c

#include <stdio.h>
#include <string.h>

void similar_str( const char* txt1, int len1, const char* txt2, int len2, int* pos1, int* pos2, int* max, int* count ) {
    *max = 0;
    *count = 0;
    for ( int i = 0; i < len1; i++ ) {
        for ( int j = 0; j < len2; j++ ) {
            int l = 0;
            
            while ( ( i + l < len1 ) && ( j + l < len2 ) && ( txt1[ i + l ] == txt2[ j + l ] ) ) {
                l++;
            }
            
            if ( l > *max ) {
                *max = l;
                *count += 1;
                *pos1 = i;
                *pos2 = j;
            }
        }
    }
}

int similar_char( const char* txt1, int len1, const char* txt2, int len2 ) {
    int sum = 0;
    int pos1 = 0;
    int pos2 = 0;
    int max = 0;
    int count = 0;

    similar_str( txt1, len1, txt2, len2, &pos1, &pos2, &max, &count );

    sum = max;
    if ( pos1 && pos2 && count > 1 ) {
        char sub1[pos1 + 1];
        strncpy( sub1, txt1, pos1 );
        sub1[pos1] = '\0';
        
        char sub2[pos2 + 1];
        strncpy( sub2, txt2, pos2 );
        sub2[pos2] = '\0';
        
        sum += similar_char( sub1, pos1, sub2, pos2 );
    }

    if ( ( pos1 + max < len1) && ( pos2 + max < len2 ) ) {
        char sub1[len1 - pos1 - max + 1];
        strncpy(sub1, txt1 + pos1 + max, len1 - pos1 - max);
        sub1[len1 - pos1 - max] = '\0';
        
        char sub2[len2 - pos2 - max + 1];
        strncpy(sub2, txt2 + pos2 + max, len2 - pos2 - max);
        sub2[len2 - pos2 - max] = '\0';
        
        sum += similar_char( sub1, len1 - pos1 - max, sub2, len2 - pos2 - max );
    }

    return sum;
}

int main() {
    const char* txt1 = "hello";
    const char* txt2 = "hallo";
    printf( "%d\n", similar_char( txt1, strlen(txt1), txt2, strlen(txt2) ) );
    return 0;
}

smilar.php

<?php

function similar_str(string $txt1, int $len1, string $txt2, int $len2, &$pos1, &$pos2, &$max, &$count) {
    $max = 0;
    $count = 0;
    for ( $i = 0; $i < $len1; $i++ ) {
        for ( $j = 0; $j < $len2; $j++ ) {
            $l = 0;
            
            while ( ( $i + $l < $len1 ) && ( $j + $l < $len2 ) && ( $txt1[ $i + $l ] === $txt2[ $j + $l ] ) ) {
                $l++;
            }
            
            if ( $l > $max ) {
                $max = $l;
                $count += 1;
                $pos1 = $i;
                $pos2 = $j;
            }
        }
    }
}

function similar_char( string $txt1, int $len1, string $txt2, int $len2 ): int {
    $sum = 0;
    $pos1 = 0;
    $pos2 = 0;
    $max = 0;
    $count = 0;

    similar_str( $txt1, $len1, $txt2, $len2, $pos1, $pos2, $max, $count );

    if ( $sum = $max ) {
        if ( $pos1 && $pos2 && $count > 1 ) {
            $sum += similar_char(
            	substr($txt1, 0, $pos1),
            	$pos1,
            	substr($txt2, 0, $pos2),
            	$pos2
            );
        }

        if ( ( $pos1 + $max < $len1 ) && ( $pos2 + $max < $len2 ) ) {
            $sum += similar_char(
            	substr( $txt1, $pos1 + $max ),
            	$len1 - $pos1 - $max,
				substr( $txt2, $pos2 + $max ), $len2 - $pos2 - $max
			);
        }
    }

    return $sum;
}

$txt1 = "hello";
$txt2 = "hallo";

echo similar_char( $txt1, strlen( $txt1 ), $txt2, strlen( $txt2 ) );

smilar.py

def similar_str(txt1, len1, txt2, len2):
    max_length = 0
    count = 0
    pos1 = pos2 = 0
    
    for i in range(len1):
        for j in range(len2):
            l = 0
            
            while (i + l < len1) and (j + l < len2) and (txt1[i + l] == txt2[j + l]):
                l += 1
            
            if l > max_length:
                max_length = l
                count += 1
                pos1, pos2 = i, j
    
    return pos1, pos2, max_length, count

def similar_char(txt1, len1, txt2, len2):
    sum_ = 0
    pos1, pos2, max_length, count = similar_str(txt1, len1, txt2, len2)
    
    if max_length > 0:
        sum_ = max_length
        if pos1 and pos2 and count > 1:
            sum_ += similar_char(txt1[:pos1], pos1, txt2[:pos2], pos2)
        
        if (pos1 + max_length < len1) and (pos2 + max_length < len2):
            sum_ += similar_char(txt1[pos1 + max_length:], len1 - pos1 - max_length, txt2[pos2 + max_length:], len2 - pos2 - max_length)
    
    return sum_

txt1 = "hello"
txt2 = "hallo"

print(similar_char(txt1, len(txt1), txt2, len(txt2)))