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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.

Solution:

class Solution {
    public String mergeAlternately(String word1, String word2) {
       StringBuilder sb = new StringBuilder();
       int n = word1.length();
       int m = word2.length();

       int i = 0;
       int j = 0;

       while(i < n && j < m){
        sb.append(word1.charAt(i));
        sb.append(word2.charAt(j));
        i++;
        j++;
       }

       while(i < n){
        sb.append(word1.charAt(i));
        i++;
       }


       while(j < m){
        sb.append(word2.charAt(j));
        j++;
       }


       return sb.toString();
    }
}

// TC: O(n)
// SC: O(n)