refactor 14

Author: fishercoder1534

README.md

@@ -27,7 +27,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |737|[Sentence Similarity II](https://leetcode.com/problems/sentence-similarity-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_737.java) | O(nlogk + k) n is the length of max(words1, words2), k is the length of pairs| O(k) | Medium| Union Find
 |735|[Asteroid Collision](https://leetcode.com/problems/asteroid-collision/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_735.java) | O(n) | O(n) | Medium | Stack
 |734|[Sentence Similarity](https://leetcode.com/problems/sentence-similarity/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_734.java) | O(n*k) | O(1) | Easy | HashTable
-|733|[Flood Fill](https://leetcode.com/problems/flood-fill/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_733.java) | O(m*n) | O(m*n) | Easy | BFS, DFS
+|733|[Flood Fill](https://leetcode.com/problem**__**s/flood-fill/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_733.java) | O(m*n) | O(m*n) | Easy | BFS, DFS
 |729|[My Calendar I](https://leetcode.com/problems/my-calendar-i/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_729.java) | O(n) | O(n) | Medium |
 |728|[Self Dividing Numbers](https://leetcode.com/problems/self-dividing-numbers/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_728.java) | O(n*k) k is the average number of digits of each number in the given array| O(1) | Easy | 
 |727|[Minimum Window Subsequence](https://leetcode.com/problems/minimum-window-subsequence/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_727.java) | O(m*n) | O(m*n) | Hard | DP
@@ -653,7 +653,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_17.java)|O(n*4^n)|O(n)|Medium|Backtracking
 |16|[3Sum Closest](https://leetcode.com/problems/3sum-closest/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_16.java)|O(nlogn)|O(1)|Medium|Two Pointers
 |15|[3Sum](https://leetcode.com/problems/3sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_15.java)|O(n^2)|O(1)|Medium|Two Pointers, Binary Search
-|14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_14.java)| O(n*min(wordLength in this array)) | O(1) | Easy
+|14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_14.java)| O(S) (S is the sum of all characters in all strings) | O(1) | Easy
 |13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer)|[Solution](../master/src/main/java/com/fishercoder/solutions/_13.java)| O(1) | O(1) | Easy | Math, String
 |12|[Integer to Roman](https://leetcode.com/problems/integer-to-roman/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_12.java)|O(1)|O(1)|Medium| Math, String
 |11|[Container With Most Water](https://leetcode.com/problems/container-with-most-water/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_11.java)|O(n)|O(1)|Medium|

src/main/java/com/fishercoder/solutions/_14.java

@@ -16,7 +16,7 @@ public String longestCommonPrefix(String[] strs) {
 
             int i = 0;
             String prefix = "";
-            String result = "";
+            String result;
             boolean broken = false;
             while (true) {
                 i++;
@@ -39,4 +39,40 @@ public String longestCommonPrefix(String[] strs) {
         }
     }
 
+    public static class Solution2 {
+        //horizontal scan
+        public String longestCommonPrefix(String[] strs) {
+            if (strs.length == 0) {
+                return "";
+            }
+            String prefix = strs[0];
+            for (int i = 1; i < strs.length; i++) {
+                while (strs[i].indexOf(prefix) != 0) {
+                    prefix = prefix.substring(0, prefix.length() - 1);
+                    if (prefix.isEmpty()) {
+                        return "";
+                    }
+                }
+            }
+            return prefix;
+        }
+    }
+
+    public static class Solution3 {
+        //vertical scan
+        public String longestCommonPrefix(String[] strs) {
+            if (strs.length == 0) {
+                return "";
+            }
+            for (int i = 0; i < strs[0].length(); i++) {
+                char c = strs[0].charAt(i);
+                for (int j = 1; j < strs.length; j++) {
+                    if (i == strs[j].length() || strs[j].charAt(i) != c) {
+                        return strs[0].substring(0, i);
+                    }
+                }
+            }
+            return strs[0];
+        }
+    }
 }

src/test/java/com/fishercoder/_14Test.java

@@ -8,17 +8,39 @@
 
 public class _14Test {
     private static _14.Solution1 solution1;
+    private static _14.Solution2 solution2;
+    private static _14.Solution3 solution3;
     private static String[] strs;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _14.Solution1();
+        solution2 = new _14.Solution2();
+        solution3 = new _14.Solution3();
     }
 
     @Test
     public void test1() {
         strs = new String[]{"a", "b"};
         assertEquals("", solution1.longestCommonPrefix(strs));
+        assertEquals("", solution2.longestCommonPrefix(strs));
+        assertEquals("", solution3.longestCommonPrefix(strs));
+    }
+
+    @Test
+    public void test2() {
+        strs = new String[]{"leetcode", "lead"};
+        assertEquals("le", solution1.longestCommonPrefix(strs));
+        assertEquals("le", solution2.longestCommonPrefix(strs));
+        assertEquals("le", solution3.longestCommonPrefix(strs));
+    }
+
+    @Test
+    public void test3() {
+        strs = new String[]{"leetcode", "code"};
+        assertEquals("", solution1.longestCommonPrefix(strs));
+        assertEquals("", solution2.longestCommonPrefix(strs));
+        assertEquals("", solution3.longestCommonPrefix(strs));
     }
 
 }