Fix longest substring without repeating characters by checking if the…

… current character has been seen before in the current window, and if so, move the start of the window to be just after the last occurance

src/3-longest-substring-without-repeating-characters/main.go

@@ -5,7 +5,7 @@ func lengthOfLongestSubstring(s string) int {
 	maxLength := 0
 	charhm := make(map[rune]int)
 	for end, char := range s {
-		if trackedIdx, found := charhm[char]; found {
+		if trackedIdx, found := charhm[char]; found && trackedIdx >= start {
 			start = trackedIdx + 1
 		}
 		charhm[char] = end