unique substrings in wraparound string

fishercoder1534 · fishercoder1534 · commit 204d8430df55 · 2016-12-04T11:23:57.000-08:00
diff --git a/MEDIUM/src/medium/UniqueSubstringsinWraparoundString.java b/MEDIUM/src/medium/UniqueSubstringsinWraparoundString.java
@@ -0,0 +1,38 @@
+package medium;
+
+public class UniqueSubstringsinWraparoundString {
+    /**A naive solution would definitely result in TLE.
+     * Since the pattern keeps repeating, DP is the way to go.
+     * Because the input consists merely of lowercase English letters, we could maintain an array of size 26,
+     * keep updating this array, counting the substrings that end with this letter, keep updating it with the largest one possible.
+     * 
+     * Inspired by this: https://discuss.leetcode.com/topic/70658/concise-java-solution-using-dp*/
+    public static int findSubstringInWraproundString(String p) {
+        if (p == null || p.isEmpty()) return 0;
+        if (p.length() < 2) return p.length();
+        int count = 0;
+        int[] dp = new int[26];
+        dp[p.charAt(0) - 'a'] = 1;
+        int len = 1;
+        for (int i = 1; i < p.length(); i++) {
+            if (p.charAt(i) - 1 == p.charAt(i-1) || (p.charAt(i) == 'a' && p.charAt(i-1) == 'z')){
+                len++;
+            } else {
+                len = 1;
+            }
+            dp[p.charAt(i) - 'a'] = Math.max(len, dp[p.charAt(i) - 'a']);
+        }
+        
+        for (int i : dp){
+            count += i;
+        }
+        return count;
+    }
+    
+    public static void main(String...args){
+//        String p = "a";
+//        String p = "abcgha";
+        String p = "zab";
+        System.out.println(findSubstringInWraproundString(p));
+    }
+}
diff --git a/README.md b/README.md
@@ -1,6 +1,7 @@
 # fishercoderLeetcode
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|467|[Unique Substrings in Wraparound String](https://leetcode.com/problems/unique-substrings-in-wraparound-string/)|[Solution](../../blob/master/MEDIUM/src/medium/UniqueSubstringsinWraparoundString.java) | O(n) |O(1) | Medium| DP
 |463|[Island Perimeter](https://leetcode.com/problems/island-perimeter/)|[Solution](../../blob/master/EASY/src/easy/IslandPerimeter.java)| O(m*n)|O(1) | Easy| 
 |462|[Minimum Moves to Equal Array Elements II](https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/)|[Solution](../../blob/master/MEDIUM/src/medium/MinimumMovestoEqualArrayElementsII.java) | O(nlogn) |O(1) | Medium|
 |459|[Repeated Substring Pattern](https://leetcode.com/problems/repeated-substring-pattern/)|[Solution](../../blob/master/EASY/src/easy/RepeatedSubstringPattern.java)| O(n)|O(n) | Easy| KMP
