add solution for leetcode3

Author: swiftwind0405

README.md

@@ -407,8 +407,8 @@ LeetCode
 |8|[String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)| |Easy|
 |7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)| |Easy|
 |6|[ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)| |Easy|
-|5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substri


ng/)| |Medium|
+|5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)| |Medium|
 |4|[Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)| |Hard|
-|3|[Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)| |Medium|
+|3|[Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)| [js](./algorithms/longestSubstringWithoutRepeatingCharacters/longestSubstringWithoutRepeatingCharacters.js) |Medium|
 |2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)| [js](./algorithms/addTwoNumbers/addTwoNumbers.js) |Medium|
 |1|[Two Sum](https://leetcode.com/problems/two-sum/) | [java](./algorithms/twoSum/twoSum.java), [js](./algorithms/twoSum/twoSum.js), [python](./algorithms/twoSum/twoSum.py) |Easy|

algorithms/longestSubstringWithoutRepeatingCharacters/longestSubstringWithoutRepeatingCharacters.js

@@ -0,0 +1,22 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var lengthOfLongestSubstring = function(s) {
+    const set = new Set();
+    let R = -1, ans = 0;
+    const len = s.length;
+    for (let L = 0; L < len; L++) {
+        if (L !== 0) {
+			// 左指针向右移动一格，移除一个字符
+            set.delete(s.charAt(L - 1))
+        }
+        while ( R + 1 < len && !set.has(s.charAt(R + 1))) {
+			// 不断地移动右指针
+            set.add(s.charAt(R + 1));
+            ++R;
+        }
+        ans = Math.max(ans, R - L + 1)
+    }
+    return ans;
+};