def check_permutation(str1: str, str2: str) -> bool:
    """
    Determine if one string is a permutation of the other.

    Args:
        str1 (str): The first string.
        str2 (str): The second string.

    Returns:
        bool: True if string one is a permutation of string two.

    """
    # Check the lengths.
    if len(str1) != len(str2):
        return False

    # Check the unique characters.
    chars1 = {c: 0 for c in str1}
    chars2 = {c: 0 for c in str2}

    for c in chars1:
        if c not in chars2:
            return False

    # Sum the occurrences.
    for c in str1:
        chars1[c] += 1
    for c in str2:
        chars2[c] += 1

    # Check the occurrences.
    for c in chars1:
        if chars1[c] != chars2[c]:
            return False

    return True