Add solution for Challenge 6 by nasseredine

Author: Nasseredine Bajwa

challenge-6/submissions/nasseredine/solution-template.go

@@ -0,0 +1,43 @@
+// Package challenge6 contains the solution for Challenge 6.
+package challenge6
+
+import (
+	"strings"
+	"unicode"
+)
+
+// CountWordFrequency takes a string containing multiple words and returns
+// a map where each key is a word and the value is the number of times that
+// word appears in the string. The comparison is case-insensitive.
+//
+// Words are defined as sequences of letters and digits.
+// All words are converted to lowercase before counting.
+// All punctuation, spaces, and other non-alphanumeric characters are ignored.
+//
+// For example:
+// Input: "The quick brown fox jumps over the lazy dog."
+// Output: map[string]int{"the": 2, "quick": 1, "brown": 1, "fox": 1, "jumps": 1, "over": 1, "lazy": 1, "dog": 1}
+func CountWordFrequency(text string) map[string]int {
+	wordFrequency := make(map[string]int)
+
+	var token strings.Builder
+	for _, r := range text {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) {
+			token.WriteRune(unicode.ToLower(r))
+		} else if r != '\'' {
+			if token.Len() > 0 {
+				flushToken(wordFrequency, &token)
+			}
+		}
+	}
+	if token.Len() > 0 {
+		flushToken(wordFrequency, &token)
+	}
+
+	return wordFrequency
+}
+
+func flushToken(wordFrequency map[string]int, token *strings.Builder) {
+	wordFrequency[token.String()]++
+	token.Reset()
+}