README.md

1768. Merge Strings Alternately

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.

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.

Solutions (Rust)

1. Recursion

impl Solution {
    pub fn merge_alternately(word1: String, word2: String) -> String {
        if word1.is_empty() && word2.is_empty() {
            return String::new();
        }

        format!(
            "{}{}{}",
            word1.get(..1).unwrap_or(""),
            word2.get(..1).unwrap_or(""),
            Self::merge_alternately(
                word1.get(1..).unwrap_or("").to_string(),
                word2.get(1..).unwrap_or("").to_string()
            )
        )
    }
}