go: add «1002. Find Common Characters»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/find-common-characters.go

@@ -0,0 +1,34 @@
+package find_common_characters
+
+func commonChars(words []string) []string {
+	A := int('a')
+	countCharacters := func(counters []int, word string) {
+		for _, c := range word {
+			counters[int(c)-A]++
+		}
+	}
+	setCommon := func(common []int, word []int) {
+		for i, count := range word {
+			common[i] = min(common[i], count)
+		}
+	}
+
+	commonCounters := make([]int, 26)
+	countCharacters(commonCounters, words[0])
+
+	for _, word := range words {
+		wordCounters := make([]int, 26)
+
+		countCharacters(wordCounters, word)
+		setCommon(commonCounters, wordCounters)
+	}
+
+	var result []string
+	for i, count := range commonCounters {
+		for count > 0 {
+			result = append(result, string(rune(A+i)))
+			count--
+		}
+	}
+	return result
+}