Boyer-Moore-Horspool (Go)

count_words.go

package main

import (
    "fmt"
)

func count_words(word, text string) int {
    var skip [255]int

    m := len(word)
    n := len(text)

    if m > n {
        return 0
    }

    //Initializing skip table
    for i := 0; i <= 254; i++ {
        skip[i] = m
    }

    //Adding skip table values
    for k := 0; k < m - 1; k++ {
        skip[int(word[k])] = m - k - 1
    }

    k := m - 1
    count := 0
    for k < n {
        j := m - 1
        i := k
        for j >= 0 && text[i] == word[j] { j--; i-- } //The matching process
        if j == -1 { // Found a match, increase the counter and skip forward
            //Calculate the begining of the word
            begin := text[0]
            if i > 0 {
                begin = text[i]
            }

            //Calculate the end of the word
            end := text[len(text) - 1]
            if i + m + 1 < n {
                end = text[i + m + 1]
            }
            //Check if it's a word
            if (end == ' ' && i == -1 ) || (i == n - m - 1 && begin == ' ') || (begin == ' ' && end == ' ') {
                count++
                k += m - 1
                continue
            }
        }
        // No match found, skip forward
        k += skip[text[k]]
    }
    return count
}

func main() {
    //fmt.Printf("Position: %d\n", count_words("aaaa", "bbbbbbbb"))
    fmt.Printf("Result: %d\n\n", count_words("aaaa", "bbbbbaaaaa"))
    fmt.Printf("Result: %d\n", count_words("111", 
                                    "aaddaaaaa 11111aaaaaaaaaaddaaa"))
}