#include <cassert>
#include <cstddef>
#include <iostream>

// Two strings may either be equal or unequal.
// This Boolean-valued question may be answered
// by simply going through the two strings until
// two characters are found that are unequal.
//
// We may instead ask the question:
//
//     "How different are two strings?"
//
// One way of describing how different two strings
// of equal length are is the Hamming distance.
//
// The Hamming distance between two strings of equal
// length is the number of positions at which the
// corresponding characters differ.
//
// For example, the Hamming distance between
//
//     "Hay"
//     "Day"
//
// is 1.
//
// The Hamming distance is defined here only for
// strings of equal length. Your function should
// therefore assert that the two strings have the
// same length.

// Function declarations
std::size_t hamming_distance(
    char const str1[],
    char const str2[]
);

int main();

// Function definitions
int main() {
    std::cout << hamming_distance(
        "Hi", "SI"
    ) << std::endl;

    std::cout << hamming_distance(
        "Hay", "Day"
    ) << std::endl;

    std::cout << hamming_distance(
        "These are equal", "These are equal"
    ) << std::endl;

    std::cout << hamming_distance(
        "These aren't equal", "These are unequal."
    ) << std::endl;

    return 0;
}

std::size_t hamming_distance(
    char const str1[],
    char const str2[]
) {
    // Enter your implementation here.
    return 0;
}














































// You do not need to determine the lengths of the
// two strings before calculating the Hamming distance.
//
// Continue while neither string has reached its null
// character. For each pair of corresponding characters,
// increase the distance if they are different.
//
// Once either string ends, what must be true if the
// two strings have the same length?














































// Here is one solution:

/*
std::size_t hamming_distance(
    char const str1[],
    char const str2[]
) {
    std::size_t distance{ 0 };
    std::size_t k{ 0 };

    while ( (str1[k] != '\0') && (str2[k] != '\0') ) {
        if ( str1[k] != str2[k] ) {
            ++distance;
        }

        ++k;
    }

    // The Hamming distance is defined here only for
    // strings of equal length. Therefore, if either
    // string has ended, the other must end at the
    // same position.
    assert( (str1[k] == '\0') && (str2[k] == '\0') );

    return distance;
}
*/