PHP 거듭제곱의 합

1 개요

PHP 거듭제곱의 합

sum_of_powers.php

<?php
function sum_of_powers($n, $power)
{
    $sum = 0;
    for ($i = 1; $i <= $n; $i++) {
        $sum += $i ** $power;
    }
    return $sum;
}

function sum_by_fomular($n, $power)
{
    if ($power == 0) return $n;
    if ($power == 1) return ($n * ($n + 1)) / 2.0;
    if ($power == 2) return ($n * ($n + 1) * (2 * $n + 1)) / 6.0;
    if ($power == 3) return (($n + 1) * $n / 2.0) ** 2;
    if ($power == 4) return ($n * ($n + 1) * (2 * $n + 1) * (3 * $n ** 2 + 3 * $n - 1)) / 30.0;
    return false;
}

$n = 4;
echo "[n = $n]\n";
echo "power\tsum1\tsum2\n";
for ($power = 0; $power <= 4; $power++) {
    $sum1 = sum_of_powers($n, $power);
    $sum2 = sum_by_fomular($n, $power);
    echo "$power\t$sum1\t$sum2\n";
}

실행결과

$ php sum_of_powers.php 
[n = 4]
power	sum1	sum2
0	4	4
1	10	10
2	30	30
3	100	100
4	354	354

2 같이 보기

• 거듭제곱의 합