[Sync Iteration] go/parallel-letter-frequency/1

solutions/go/parallel-letter-frequency/1/parallel_letter_frequency.go

@@ -0,0 +1,41 @@
+package letter
+
+import "sync"
+
+// FreqMap records the frequency of each rune in a given text.
+type FreqMap map[rune]int
+
+// Frequency counts the frequency of each rune in a given text and returns this
+// data as a FreqMap.
+func Frequency(text string) FreqMap {
+	frequencies := FreqMap{}
+	for _, r := range text {
+		frequencies[r]++
+	}
+	return frequencies
+}
+
+// ConcurrentFrequency counts the frequency of each rune in the given strings,
+// by making use of concurrency.
+func ConcurrentFrequency(texts []string) FreqMap {
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+
+	m := make(FreqMap)
+	for _, line := range texts {
+		wg.Add(1)
+		go func(line string) {
+			defer wg.Done()
+
+			for _, r := range line {
+				mu.Lock()
+				m[r]++
+				mu.Unlock()
+			}
+		}(line)
+	}
+
+	wg.Wait()
+
+	return m
+}