1768.Merge Strings Alternately
===

###### tags: `Easy`,`String`,`Two Pointers`

[1768. Merge Strings Alternately](https://leetcode.com/problems/merge-strings-alternately/)

### 題目描述

You are given two strings `word1` and `word2`. Merge the strings by adding letters in alternating order, starting with `word1`. If a string is longer than the other, append the additional letters onto the end of the merged string.

Return *the merged string*.

### 範例

**Example 1:**

Input: word1 = "abc", word2 = "pqr"
Output: "apbqcr"
Explanation: The merged string will be merged as so:
word1:  a   b   c
word2:    p   q   r
merged: a p b q c r

**Example 2:**

Input: word1 = "ab", word2 = "pqrs"
Output: "apbqrs"
Explanation: Notice that as word2 is longer, "rs" is appended to the end.
word1:  a   b 
word2:    p   q   r   s
merged: a p b q   r   s

**Example 3:**

Input: word1 = "abcd", word2 = "pq"
Output: "apbqcd"
Explanation: Notice that as word1 is longer, "cd" is appended to the end.
word1:  a   b   c   d
word2:    p   q 
merged: a p b q c   d

**Constraints**:

* 1 <= `word1.length`, `word2.length` <= 100
* `word1` and `word2` consist of lowercase English letters.

### 解答
#### Javascript

function mergeAlternately(word1, word2) {
  const result = [];
  for (let i = 0; i < 100; i++) {
    if (!word1[i] && !word2[i]) break;
    result.push(word1[i] ?? '');
    result.push(word2[i] ?? '');
  }

  return result.join('');
}

> [name=Marsgoat][time=Apr 18, 2023]

#### Python

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        ans = []

        for ch1, ch2 in zip_longest(word1, word2, fillvalue=''):
            ans.append(ch1 + ch2)

        return "".join(ans)

上面邏輯縮成一行

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        return "".join(ch1 + ch2 for ch1, ch2 in zip_longest(word1, word2, fillvalue=''))

> [name=Ron Chen][time=Tue, Apr 18, 2023]

#### Java
練習 Java Stream API

class Solution {
    public String mergeAlternately(String word1, String word2) {
        StringBuilder sb = new StringBuilder();
        IntStream.range(0, Math.min(word1.length(), word2.length()))
                 .forEach(i -> sb.append(word1.charAt(i))
                                 .append(word2.charAt(i)));

        if(word1.length() > word2.length()) {
            sb.append(word1.substring(word2.length()));
        } else {
            sb.append(word2.substring(word1.length()));
        }

        return sb.toString();
    }
}

> [name=Ron Chen][time=Tue, Apr 18, 2023]

#### TypeScript

function mergeAlternately(word1: string, word2: string): string {
  let result = '';

  if (word1.length >= word2.length) {
    for (let i = 0; i < word1.length; i++) {
      result += word1.charAt(i);
      result += word2.charAt(i);
    }
  } else {
    for (let i = 0; i < word2.length; i++) {
      result += word1.charAt(i);
      result += word2.charAt(i);
    }
  }

  return result;
}

> Note: `String.prototype.charAt()` 如果超過索引值會回傳空字串
> [name=Sheep][time=Apr 18, 2023]

### Reference

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