<s>Human: 给定两个字符串a和b，创建一个函数，该函数返回由a和b中按字典序交替构成的新字符串。
a = "abcd"b = "efgh"# TODO: create function to alternate characters
</s><s>Assistant: def alternate_strings(a, b):
    result = ""
    min_len = min(len(a), len(b))
    for i in range(min_len):
        result += a[i] + b[i]
    result += a[min_len:] + b[min_len:]
    return result

# Example usage
a = "abcd"
b = "efgh"
print(alternate_strings(a, b)) # Output: "aebfcgdh"
</s>