Add Longest Substring solution

Author: lon-io

longest_substring.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+    "fmt"
+    "strings"
+)
+
+func lengthOfLongestSubstring(s string) int {
+    longest := ""
+    current := ""
+
+    for _, v := range s {
+		vStr := string(v)
+
+		// Faster
+        oldIndex := strings.Index(current, vStr)
+        if oldIndex > -1 {
+			fmt.Printf("\nFound %s at %d, Resetting %s to: %s", vStr, oldIndex, current, current[oldIndex + 1:])
+            current = current[(oldIndex + 1):]
+        }
+
+        current += string(vStr)
+
+        if len(current) > len(longest) {
+            longest = current
+        }
+    }
+
+	fmt.Printf("\nLongest String: %s", longest)
+    return len(longest)
+}
+
+func main() {
+	test1 := "pwwkew"
+	test2 := "dvdf"
+	fmt.Printf("\n%d", lengthOfLongestSubstring(test1))
+	fmt.Printf("\n%d", lengthOfLongestSubstring(test2))
+}