Sergio Alves

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.

PHP Code

class Solution {

    /**
     * @param String $word1
     * @param String $word2
     * @return String
     */
    function mergeAlternately($word1, $word2) {
           
    	$w1 = str_split($word1);
    	$w2 = str_split($word2);

        if (strlen($word1) <= strlen($word2)) {
        	$shorter_word = $w1;
        	$end_of_string = substr($word2, strlen($word1), strlen($word2) - strlen($word1));
        } else {
        	$shorter_word = $w2;
        	$end_of_string = substr($word1, strlen($word2), strlen($word1) - strlen($word2));
        }
    	
    	$o = "";
        for($i = 0; $i < count($shorter_word); $i++) {
        	$o .= $w1[$i] . $w2[$i];
        }
        
        $o .= $end_of_string;
        return $o;
    }
}