Algorithm Puzzles: Merge Strings Alternately

Algorithm Puzzles everyday every week sometimes: Merge Strings Alternately

Puzzle

Puzzle from leetcode:

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

Solution

Two pointer:

class Solution:
    def mergeAlternately(self, word1: str, word2: str) -> str:
        len1, len2 = len(word1), len(word2)
        i1 = i2 = 0
        ret = ""
        while i1 < len(word1) and i2 < len(word2):
            ret += word1[i1]
            ret += word2[i2]
            i1 += 1
            i2 += 1

        ret += word1[i1:] if i1 < len1 else word2[i2:]
        return ret

T.C.: O(N)