go: add «1371. Find the Longest Substring Containing Vowels in Even Counts»

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

go/find-the-longest-substring-containing-vowels-in-even-counts.go

@@ -0,0 +1,40 @@
+package main
+
+func findTheLongestSubstring(s string) int {
+	getMask := func(c rune) int {
+		switch c {
+		case 'a':
+			return 1
+		case 'e':
+			return 2
+		case 'i':
+			return 4
+		case 'o':
+			return 8
+		case 'u':
+			return 16
+		default:
+			return 0
+		}
+	}
+
+	longest := 0
+
+	indices := make([]int, 32)
+	for i, _ := range indices {
+		indices[i] = -1
+	}
+
+	xor := 0
+	for i, c := range s {
+		xor ^= getMask(c)
+
+		if indices[xor] == -1 && xor != 0 {
+			indices[xor] = i
+		}
+
+		longest = max(longest, i-indices[xor])
+	}
+
+	return longest
+}