# Javascript in Leetcode 13–15|面試問題

### 目錄

- 13-Roman-to-Integer
- 14-Longest-Common-Prefix
- 15–3Sum

找到source code | Github

### 13. Roman to Integer

Roman numerals are represented by seven different symbols: `I`

, `V`

, `X`

, `L`

, `C`

, `D`

and `M`

.

Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000

For example, `2`

is written as `II`

in Roman numeral, just two ones added together. `12`

is written as `XII`

, which is simply `X + II`

. The number `27`

is written as `XXVII`

, which is `XX + V + II`

.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`

. Instead, the number four is written as `IV`

. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`

. There are six instances where subtraction is used:

`I`

can be placed before`V`

(5) and`X`

(10) to make 4 and 9.`X`

can be placed before`L`

(50) and`C`

(100) to make 40 and 90.`C`

can be placed before`D`

(500) and`M`

(1000) to make 400 and 900.

Given a roman numeral, convert it to an integer.

**Example 1:**

Input: s = "III" Output: 3 Explanation: III = 3.

**Example 2:**

Input: s = "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3.

**Example 3:**

Input: s = "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

**Constraints:**

`1 <= s.length <= 15`

`s`

contains only the characters`('I', 'V', 'X', 'L', 'C', 'D', 'M')`

.- It is
**guaranteed**that`s`

is a valid roman numeral in the range`[1, 3999]`

.

### 14. 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.

**Constraints:**

`1 <= strs.length <= 200`

`0 <= strs[i].length <= 200`

`strs[i]`

consists of only lowercase English letters.

### 15. 3Sum

Given an integer array nums, return all the triplets `[nums[i], nums[j], nums[k]]`

such that `i != j`

, `i != k`

, and `j != k`

, and `nums[i] + nums[j] + nums[k] == 0`

.

Notice that the solution set must not contain duplicate triplets.

**Example 1:**

Input: nums = [-1,0,1,2,-1,-4] Output: [[-1,-1,2],[-1,0,1]]

**Example 2:**

Input: nums = [] Output: []

**Example 3:**

Input: nums = [0] Output: []

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