Merge Strings Alternately

1package pkg5leetcode.official75;2 3/*4 * Merge Strings Alternately | LC 17685 * APPROACH: Two pointers append from word1 and word2 alternately.6 * COMPLEXITY: Time O(m+n), Space O(m+n)7 */8public class official75_LC1768MergeStringsAlternately {9    static String mergeAlternately(String word1, String word2) {10        StringBuilder sb = new StringBuilder();11        int i = 0, j = 0;12        while (i < word1.length() || j < word2.length()) {13            if (i < word1.length()) sb.append(word1.charAt(i++));14            if (j < word2.length()) sb.append(word2.charAt(j++));15        }16        return sb.toString();17    }18 19    public static void main(String[] args) {20        check("apbqcr".equals(mergeAlternately("abc", "pqr")), "case1");21        check("apbqrs".equals(mergeAlternately("ab", "pqrs")), "case2");22        System.out.println("all tests passed");23    }24 25    static void check(boolean cond, String name) {26        if (!cond) throw new AssertionError("FAILED: " + name);27        System.out.println("  PASS " + name);28    }29}