add: longest common prefix (ignacio-chiazzo#52)

* add: longest common prefix

* add: test

Co-authored-by: ongch <ongch@sea.com>
Co-authored-by: Ignacio Chiazzo Cardarello <ignaciochiazzo@gmail.com>

Author: 3 people

LeetcodeProblems/Algorithms/Longest_Common_Prefix.js

@@ -0,0 +1,34 @@
+/**
+Longest Common Prefix
+https://leetcode.com/problems/longest-common-prefix/
+
+Write a function to find the longest common prefix string amongst an array of strings.
+
+If there is no common prefix, return an empty string "".
+
+Example 1:
+Input: strs = ["flower","flow","flight"]
+Output: "fl"
+
+Example 2:
+Input: strs = ["dog","racecar","car"]
+Output: ""
+Explanation: There is no common prefix among the input strings.
+
+*/
+
+/**
+ * @param {string[]} strs
+ * @return {string}
+ */
+ var longestCommonPrefix = function(strs) {
+  if(strs.length === 0) return "";
+  
+  return strs.reduce((result, curr)=>{
+      let i = 0;
+      while(result[i] && curr[i] && result[i] === curr[i]) i++;
+      return result.slice(0, i);
+  });
+};
+
+module.exports.longestCommonPrefix = longestCommonPrefix;

LeetcodeProblemsTests/Algorithms/Longest_Common_Prefix_Test.js

@@ -0,0 +1,11 @@
+
+const assert = require('assert');
+const longestCommonPrefix = require('../../LeetcodeProblems/Algorithms/Longest_Common_Prefix').longestCommonPrefix;
+
+function test() {
+  assert.equal(longestCommonPrefix(["flower","flow","flight"]), "fl");
+  assert.equal(longestCommonPrefix(["dog","racecar","car"]), "");
+  assert.equal(longestCommonPrefix([]), "");
+}
+
+module.exports.test = test;

README.md

@@ -79,6 +79,7 @@ To run a specific problem in your console run  `node <problem_file_path>` (e.g.
 | [Binary Gap ](/LeetcodeProblems/Algorithms/Binary_Gap.js)                                                       | Easy   | https://leetcode.com/problems/binary-gap/ |
 | [Binary Gap ](/LeetcodeProblems/Algorithms/Binary_Gap.js)                                                       | Easy   | https://leetcode.com/problems/binary-gap/ |
 | [Majority Element](/LeetcodeProblems/Algorithms/Majority_Element.js)                                            | Easy   | https://leetcode.com/problems/majority-element/ |
+| [Longest Common Prefix](/LeetcodeProblems/Algorithms/Longest_Common_Prefix.js)                                  | Easy   | https://leetcode.com/problems/longest-common-prefix/ |
 | [Two Sum](/LeetcodeProblems/Algorithms/2Sum.js)                                                                 | Easy   | https://leetcode.com/problems/two-sum/ |
 | [Tic Tac Toe ](/LeetcodeProblems/Algorithms/Tic_Tac_Toe.js)                                                     |        | |
 | [Permutations With Duplicates ](/LeetcodeProblems/Algorithms/Permutations_With_Duplicates.js)                   |        | |