add: 最长公共前缀

.vscode/settings.json

@@ -26,6 +26,8 @@
     "preorder",
     "pwwkew",
     "qian",
+    "racecar",
+    "strs",
     "subarray",
     "subarrays",
     "umghlrlose",

README.md

@@ -117,6 +117,11 @@ LeetCode 与 LintCode 解题记录。此为个人练习仓库，代码中对重
 
   - LeetCode 5417. 定长子串中元音的最大数目 <https://leetcode-cn.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length/>
 
+- [最长公共前缀](src/string/longest-common-prefix.js)
+
+  - LeetCode 14. 最长公共前缀 <https://leetcode-cn.com/problems/longest-common-prefix/>
+  - LintCode 78. 最长公共前缀 <https://www.lintcode.com/problem/longest-common-prefix/description>
+
 ## 数组/队列/集合/映射
 
 - [电话号码的字母组合](src/array/letter-combinations-of-a-phone-number.js)

src/string/longest-common-prefix.js

@@ -0,0 +1,27 @@
+const comp = (left, right, res) => {
+  if (left.length > right.length) {
+    [left, right] = [right, left]
+  }
+
+  res = res || left
+  while (right.indexOf(res) !== 0 && res.length > 0) {
+    res = res.slice(0, res.length - 1)
+  }
+
+  return res
+}
+
+/**
+ * @param {string[]} strs
+ * @return {string}
+ */
+export const longestCommonPrefix = function (strs) {
+  if (strs.length < 2) return strs[0] || ''
+
+  let res = strs[0]
+  for (let i = 1; i < strs.length; i++) {
+    res = comp(res, strs[i])
+  }
+
+  return res
+}

test/string/longest-common-prefix.test.js

@@ -0,0 +1,8 @@
+import { longestCommonPrefix } from '../../src/string/longest-common-prefix'
+
+test('最长公共前缀', () => {
+  expect(longestCommonPrefix(['flower', 'flow', 'flight'])).toBe('fl')
+  expect(longestCommonPrefix(['dog', 'racecar', 'car'])).toBe('')
+  expect(longestCommonPrefix(['a'])).toBe('a')
+  expect(longestCommonPrefix(['caa', '', 'a', 'acb'])).toBe('')
+})