fd

Author: liwentian

doc/Summary.md

@@ -9,4 +9,7 @@
  - **207. Course Schedule**
  - **210. Course Schedule II**
  - **269. Alien Dictionary**
+ 
+ # BackTracking
+ - **10. Regular Expression Matching**
 

google/RECORDS.md

@@ -1,13 +1,10 @@
 2017-9-3
 
-`
-332. Reconstruct Itinerary(Pending)
-`
 310. Minimum Height Trees
 399. Evaluate Division
 261. Graph Valid Tree
 323. Number of Connected Components in an Undirected Graph
-
+10. Regular Expression Matching
 
 2017-9-2
 329. Longest Increasing Path in a Matrix

google/src/main/java/com/leetcode/google/RegularExpressionMatching.java

@@ -0,0 +1,29 @@
+package com.leetcode.google;
+
+/**
+ * Created by liwentian on 2017/9/3.
+ */
+
+public class RegularExpressionMatching {
+
+    public boolean isMatch(String s, String p) {
+        if (p.isEmpty()) {
+            return s.isEmpty();
+        }
+        if (p.length() == 1) {
+            return s.length() == 1 && equals(s, p);
+        }
+        if (p.charAt(1) != '*') {
+            return s.length() > 0 && equals(s, p) && isMatch(s.substring(1), p.substring(1));
+        }
+        if (s.isEmpty() || !equals(s, p)) {
+            return isMatch(s, p.substring(2));
+        } else {
+            return isMatch(s, p.substring(2)) || isMatch(s.substring(1), p);
+        }
+    }
+
+    private boolean equals(String s, String p) {
+        return p.charAt(0) == '.' || s.charAt(0) == p.charAt(0);
+    }
+}