Roman Numeral in Php (original) (raw)

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Published on 14 October 2019 (Updated: 09 May 2022)

Roman Numeral in Php

Welcome to the Roman Numeral in Php page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

<?php

/**
 * Roman numeral string to Decimal value.
 * @param string $romans String to convert.
 * @return int The decimal value.
 * @throws Exception on invalid roman string.
 */
function roman_to_decimal($romans)
{
    // conversion table
    $roman_values = array("I" => 1, "V" => 5, "X" => 10,
        "L" => 50, "C" => 100, "D" => 500, "M" => 1000);

    $total = 0;
    $previous = 0;

    // parse from end to start of string
    for ($i = strlen($romans) - 1; <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mo>&gt;</mo><mo>=</mo><mn>0</mn><mo separator="true">;</mo><mo>−</mo><mo>−</mo></mrow><annotation encoding="application/x-tex">i &gt;= 0; --</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6986em;vertical-align:-0.0391em;"></span><span class="mord mathnormal">i</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">&gt;=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.8389em;vertical-align:-0.1944em;"></span><span class="mord">0</span><span class="mpunct">;</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord">−</span><span class="mord">−</span></span></span></span>i) {

        // check if the character is a roman numeral
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><mi>u</mi><mi>m</mi><mi>e</mi><mi>r</mi><mi>a</mi><mi>l</mi><mo>=</mo><mi>s</mi><mi>t</mi><mi>r</mi><mi>t</mi><mi>o</mi><mi>u</mi><mi>p</mi><mi>p</mi><mi>e</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">numeral = strtoupper(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">n</span><span class="mord mathnormal">u</span><span class="mord mathnormal">m</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">t</span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal">pp</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mopen">(</span></span></span></span>romans[$i]);
        if (!array_key_exists($numeral, $roman_values)) {
            throw new Exception("invalid string of roman numerals");
        }

        // convert to decimal and add/subtract from total.
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>v</mi><mi>a</mi><mi>l</mi><mi>u</mi><mi>e</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">value = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">v</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">u</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>roman_values[$numeral];
        if ($value >= $previous) {
            <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>l</mi><mo>+</mo><mo>=</mo></mrow><annotation encoding="application/x-tex">total += </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">o</span><span class="mord mathnormal">t</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord">+</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>value;

        } else {
            <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>l</mi><mo>−</mo><mo>=</mo></mrow><annotation encoding="application/x-tex">total -= </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">o</span><span class="mord mathnormal">t</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord">−</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>value;
        }

        // keep track of last value
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mi>r</mi><mi>e</mi><mi>v</mi><mi>i</mi><mi>o</mi><mi>u</mi><mi>s</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">previous = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">p</span><span class="mord mathnormal">re</span><span class="mord mathnormal" style="margin-right:0.03588em;">v</span><span class="mord mathnormal">i</span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal">s</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>value;
    }

    return $total;
}

try {

    // Check argument count
    if ($argc < 2) {
        echo "Usage: please provide a string of roman numerals\n";
        exit(1);
    }

    // Convert the string
    echo roman_to_decimal($argv[1]), "\n";
    exit(0);

} catch (Exception $e) {
    echo "Error: ", $e->getMessage(), "\n";
    exit(1);
}

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