longest substring without repeating characters

Author: fishercoder1534

MEDIUM/src/medium/LongestSubstringWithoutRepeatingCharacters.java

@@ -0,0 +1,29 @@
+package medium;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class LongestSubstringWithoutRepeatingCharacters {
+
+    public static int lengthOfLongestSubstring(String s) {
+        int result = 0;
+        Map<Character, Integer> map = new HashMap();
+        for (int i = 0, j = i; j < s.length(); ){
+            if (!map.containsKey(s.charAt(j)) || (map.containsKey(s.charAt(j)) && map.get(s.charAt(j)) == 0)){
+                map.put(s.charAt(j), 1);
+                result = Math.max(j-i+1, result);
+                j++;
+            } else {
+                map.put(s.charAt(i), map.get(s.charAt(i)) - 1);
+                i++;
+            }
+        }
+        return result;
+    }
+
+    public static void main(String...args){
+//        String s = "abcabcbb";
+        String s = "pwwkew";
+        System.out.println(lengthOfLongestSubstring(s));
+    }
+}

README.md

@@ -128,6 +128,7 @@
 |8|[String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)|[Solution](../../blob/master/EASY/src/easy/StringToInteger.java)| O(n) | O(1) | Easy
 |7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)|[Solution](../../blob/master/EASY/src/easy/ReverseInteger.java) | O(1) | O(1) | Easy | 
 |6|[ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)|[Solution](../../blob/master/EASY/src/easy/ZigZagConversion.java) | O(n) | O(n) | Easy | 
+|3|[Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)|[Solution](../../blob/master/MEDIUM/src/medium/LongestSubstringWithoutRepeatingCharacters.java) | O(n) | O(1) | Medium | HashMap, Sliding Window
 |2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)|[Solution](../../blob/master/MEDIUM/src/medium/AddTwoNumbers.java) | O(n) | O(1) | Medium | LinkedList
 |1|[Two Sum](https://leetcode.com/problems/two-sum/)|[Solution](../../blob/master/EASY/src/easy/TwoSum.java)| O(n)/O(n^2)|O(1)/O(n) | Easy| HashMap