add step4 for Longest Substring Without Repeating Characters

Author: rihib

pullrequests/longest_substring_without_repeating_characters/step4.go

@@ -0,0 +1,14 @@
+//lint:file-ignore U1000 Ignore all unused code
+package longestsubstringwithoutrepeatingcharacters
+
+func lengthOfLongestSubstring_step4(s string) int {
+	maxLength, left, seen := 0, 0, make(map[rune]int)
+	for right, r := range s {
+		if lastIndex, ok := seen[r]; ok && lastIndex >= left {
+			left = lastIndex + 1
+		}
+		seen[r] = right
+		maxLength = max(maxLength, right-left+1)
+	}
+	return maxLength
+}