package main
import (
"fmt"
"strings"
"unicode"
)
/*
Normalize a string:
- Convert letters to lowercase
- Replace any non-letter with a space
This ensures consistent word comparison.
*/
func normalize(s string) string {
var b strings.Builder
b.Grow(len(s))
for _, r := range s {
if unicode.IsLetter(r) {
b.WriteRune(unicode.ToLower(r))
} else {
b.WriteRune(' ')
}
}
return b.String()
}
/*
Extract words from a string.
This function:
- Normalizes the input
- Splits on whitespace
- Filters out empty entries
- Returns a map[string]bool acting as a set for fast lookup
*/
func extractWords(s string) map[string]bool {
normalized := normalize(s)
parts := strings.Fields(normalized)
words := make(map[string]bool, len(parts))
for _, w := range parts {
words[w] = true
}
return words
}
/*
Find common words between two strings.
This function:
- Extracts words from both strings
- Uses map lookups for efficiency
- Returns a slice of common words
*/
func findCommonWords(a, b string) []string {
wordsA := extractWords(a)
wordsB := extractWords(b)
var common []string
for w := range wordsA {
if wordsB[w] {
common = append(common, w)
}
}
return common
}
func main() {
s1 := "The quick brown fox jumps over the lazy dog."
s2 := "A lazy dog sleeps while the quick fox runs away."
common := findCommonWords(s1, s2)
fmt.Println("Common words:")
for _, w := range common {
fmt.Println(w)
}
}
/*
run:
Common words:
the
quick
fox
lazy
dog
*/
