add: Longest Common Prefix

Author: hijiangtao

README.md

@@ -14,6 +14,7 @@ This is the solutions collection of my LeetCode submissions, most of them are pr
 |7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/) | [JavaScript](./src/reverse-integer/res.js)|Easy|
 |11|[Container With Most Water](https://leetcode.com/problems/container-with-most-water/) | [JavaScript](./src/container-with-most-water/res.js)|Medium|
 |13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer/) | [JavaScript](./src/roman-to-integer/res.js)|Easy|
+|14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) | [JavaScript](./src/longest-common-prefix/res.js)|Easy|
 |17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) | [JavaScript](./src/letter-combinations-of-a-phone-number/res.js)|Medium|
 |19|[Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/) | [JavaScript](./src/remove-nth-node-from-end-of-list/res.js)|Medium|
 |22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/) | [JavaScript](./src/generate-parentheses/res.js)|Medium|

src/longest-common-prefix/res.js

@@ -0,0 +1,39 @@
+/**
+ * res.js
+ * @authors Joe Jiang ([email protected])
+ * @date    2017-04-03 20:42:30
+ * @version $Id$
+ * 
+ * Problem: Write a function to find the longest common prefix string amongst an array of strings.
+ * 
+ * @param {string[]} strs
+ * @return {string}
+ */
+let longestCommonPrefix = function(strs) {
+    if (strs === '' || strs.length === 0) {
+        return '';
+    }
+    
+    let prefix = '',
+        strslen = strs.length,
+        strlen = strs[0].length;
+        
+    for (let i=0; i < strlen; i++) {
+        let jud = true;
+        
+        for (let j=1; j<strslen; j++) {
+            if (strs[j][i] === undefined || strs[j][i] !== strs[0][i]) {
+                jud = false;
+                break;
+            }
+        }
+        
+        if (jud) {
+            prefix += strs[0][i];
+        } else {
+            return prefix;
+        }
+    }
+    
+    return prefix;
+};