From 44c94e5a96f6fbc1f3d1ac9e1f9ce90898373d97 Mon Sep 17 00:00:00 2001
From: Jason Staten <code@jxs.me>
Date: Fri, 30 Sep 2022 07:27:56 -0600
Subject: [PATCH] norepeat

---
 norepeat/norepeat.go      | 30 +++++++++++++++++++++++++++++
 norepeat/norepeat_test.go | 38 +++++++++++++++++++++++++++++++++++++
 norepeat/readme.md        | 40 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 norepeat/norepeat.go
 create mode 100644 norepeat/norepeat_test.go
 create mode 100644 norepeat/readme.md

diff --git a/norepeat/norepeat.go b/norepeat/norepeat.go
new file mode 100644
index 0000000..759fd55
--- /dev/null
+++ b/norepeat/norepeat.go
@@ -0,0 +1,30 @@
+package norepeat
+
+func max(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
+
+func lengthOfLongestSubstring(s string) int {
+	positions := map[byte]int{}
+	longest := 0
+
+	for i := 0; i < len(s); i++ {
+		char := s[i]
+		pos, exists := positions[char]
+		positions[char] = i
+		longest = max(longest, len(positions))
+		if exists {
+			positions = map[byte]int{}
+			i = pos
+		}
+	}
+
+	return longest
+}
+
+func LengthOfLongestSubstring(s string) int {
+	return lengthOfLongestSubstring(s)
+}
diff --git a/norepeat/norepeat_test.go b/norepeat/norepeat_test.go
new file mode 100644
index 0000000..d31be34
--- /dev/null
+++ b/norepeat/norepeat_test.go
@@ -0,0 +1,38 @@
+package norepeat_test
+
+import (
+	"testing"
+
+	"git.jxs.me/leetgo/norepeat"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmpty(t *testing.T) {
+	result := norepeat.LengthOfLongestSubstring("")
+
+	require.Equal(t, 0, result)
+}
+
+func TestSingle(t *testing.T) {
+	result := norepeat.LengthOfLongestSubstring("a")
+
+	require.Equal(t, 1, result)
+}
+
+func TestDouble(t *testing.T) {
+	result := norepeat.LengthOfLongestSubstring("ab")
+
+	require.Equal(t, 2, result)
+}
+
+func TestRepeat(t *testing.T) {
+	result := norepeat.LengthOfLongestSubstring("dad")
+
+	require.Equal(t, 2, result)
+}
+
+func TestQuad(t *testing.T) {
+	result := norepeat.LengthOfLongestSubstring("hellllo")
+
+	require.Equal(t, 3, result)
+}
diff --git a/norepeat/readme.md b/norepeat/readme.md
new file mode 100644
index 0000000..42982e0
--- /dev/null
+++ b/norepeat/readme.md
@@ -0,0 +1,40 @@
+3. Longest Substring Without Repeating Characters
+Medium
+
+Given a string s, find the length of the longest substring without repeating characters.
+
+ 
+
+Example 1:
+
+```
+Input: s = "abcabcbb"
+Output: 3
+Explanation: The answer is "abc", with the length of 3.
+```
+
+Example 2:
+
+```
+Input: s = "bbbbb"
+Output: 1
+Explanation: The answer is "b", with the length of 1.
+```
+
+Example 3:
+
+```
+Input: s = "pwwkew"
+Output: 3
+Explanation: The answer is "wke", with the length of 3.
+Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
+```
+
+ 
+
+Constraints:
+
+    0 <= s.length <= 5 * 104
+    s consists of English letters, digits, symbols and spaces.
+
+