add: leetcode 0014 readme

leetcode/0014.Longest-Common-Prefix/README.md

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+# [14. Longest Common Prefix](https://leetcode-cn.com/problems/longest-common-prefix/)
+
+## 题目
+
+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.
+
+**Constraints:**
+
+- 1 <= strs.length <= 200
+- 0 <= strs[i].length <= 200
+- strs[i] consists of only lower-case English letters.
+
+## 题目大意
+
+编写一个函数来查找字符串数组中的最长公共前缀。
+
+如果不存在公共前缀，返回空字符串 ""。
+
+## 解题思路
+
+- 对strs按照字符串长度进行升序排序，求出strs中长度最小字符串的长度minLen
+- 逐个比较长度最小字符串与其它字符串中的字符，如果不相等就返回commonPrefix,否则就把该字符加入commonPrefix
+
+## 代码
+
+```go
+package leetcode
+
+import "sort"
+
+func longestCommonPrefix(strs []string) string {
+	sort.Slice(strs, func(i, j int) bool {
+		return len(strs[i]) <= len(strs[j])
+	})
+	minLen := len(strs[0])
+	if minLen == 0 {
+		return ""
+	}
+	var commonPrefix []byte
+	for i := 0; i < minLen; i++ {
+		for j := 1; j < len(strs); j++ {
+			if strs[j][i] != strs[0][i] {
+				return string(commonPrefix)
+			}
+		}
+		commonPrefix = append(commonPrefix, strs[0][i])
+	}
+	return string(commonPrefix)
+}
+```