Merge Strings Alternately
Easy · Two Pointers · Two Pointers · String
Problem
You are given two non-empty strings word1 and word2. Build a new string by taking letters from them in turn: the first letter of word1, then the first letter of word2, then the second letter of word1, and so on.
When one string runs out of letters, append all the remaining letters of the other one, in order.
Return the merged string.
Examples
Input: word1 = "abc", word2 = "pqr" Output: "apbqcr"
a, p, b, q, c, r.
Input: word1 = "ab", word2 = "pqrs" Output: "apbqrs"
After "apbq" word1 is used up, so "rs" is appended.
Input: word1 = "abcd", word2 = "pq" Output: "apbqcd"
After "apbq" word2 is used up, so "cd" is appended.
Constraints
- 1 <= len(word1), len(word2) <= 10^4
- word1 and word2 hold lowercase English letters
Approaches
- Two pointers — time O(n + m), space O(n + m)
Follow-up
How would you merge more than two strings in turn, skipping the ones that run out? What changes if each turn takes k letters instead of one?
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