# 14. Longest Common Prefix

### Leetcode

<https://leetcode.com/problems/longest-common-prefix/>

### 題目

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 `""`.

### 解答 <a href="#ti-jie" id="ti-jie"></a>

* **方法一**

```
var longestCommonPrefix = function(strs) {
    let output = "";
    let i = 0;
    
    if (strs.length === 1) return strs[0];
    
    while(true) {
        let str = strs[0][i];
        let j = 1;
        while(j<strs.length && i<strs[0].length) {
          if (str !== strs[j][i]) return output;
          j++;
        }
        if(i>=strs[0].length) break;
        output += str;
        i++;
    }
    return output;
};
```

Runtime: 88 ms, faster than 47.43% of JavaScript online submissions for Longest Common Prefix.

Memory Usage: 41 MB, less than 16.77% of JavaScript online submissions for Longest Common Prefix.

### 測資

```
let strs = ["flower","flow","flight"];
strs = ["dog","racecar","car"];

console.log(longestCommonPrefix(strs));
```
