Java solution 003

Author: gavinfish

java/_003LongestSubStringWithoutRepeatingCharacters.java

@@ -0,0 +1,39 @@
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Given a string, find the length of the longest substring without repeating characters.
+ * <p>
+ * Examples:
+ * Given "abcabcbb", the answer is "abc", which the length is 3.
+ * Given "bbbbb", the answer is "b", with the length of 1.
+ * Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a
+ * subsequence and not a substring.
+ * Created by drfish on 13/05/2017.
+ */
+public class _003LongestSubStringWithoutRepeatingCharacters {
+    public int lengthOfLongestSubstring(String s) {
+        if (s == null)
+            return 0;
+        if (s.length() <= 1)
+            return s.length();
+        Map<Character, Integer> map = new HashMap<>();
+        int start = -1;
+        int result = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (map.containsKey(s.charAt(i))) {
+                start = Math.max(start, map.get(s.charAt(i)));
+            }
+            map.put(s.charAt(i), i);
+            result = Math.max(result, i - start);
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        _003LongestSubStringWithoutRepeatingCharacters solution = new _003LongestSubStringWithoutRepeatingCharacters();
+        assert 3 == solution.lengthOfLongestSubstring("abcabcbb");
+        assert 1 == solution.lengthOfLongestSubstring("bbbbb");
+        assert 3 == solution.lengthOfLongestSubstring("pwwkew");
+    }
+}