test

test.php

<?php
function count_highlighted_letters($L, $N, $selections)
{
    // Initialize an array to keep track of highlighted status for each character in S
    $highlighted = array_fill(0, $L, false);

    // Process each selection
    foreach ($selections as $selection) {
        list($a, $b) = $selection;
        // Convert to 0-based index
        $a -= 1;
        $b -= 1;

        // Check if we need to highlight or un-highlight
        $highlight = false;
        for ($i = $a; $i <= $b; $i++) {
            if (!$highlighted[$i]) {
                $highlight = true;
                break;
            }
        }

        // Apply highlight or un-highlight
        for ($i = $a; $i <= $b; $i++) {
            $highlighted[$i] = $highlight;
        }
    }

    // Count the number of highlighted letters
    $highlighted_count = 0;
    foreach ($highlighted as $status) {
        if ($status) {
            $highlighted_count++;
        }
    }

    return $highlighted_count;
}

// Test cases
function run_tests()
{
    $tests = [
        [
            "input" => [
                "L" => 10,
                "N" => 3,
                "selections" => [
                    [2, 6],
                    [6, 8],
                    [3, 4]
                ]
            ],
            "expected" => 5
        ],
        [
            "input" => [
                "L" => 10,
                "N" => 10,
                "selections" => [
                    [1, 6],
                    [2, 5],
                    [1, 7],
                    [1, 7],
                    [2, 7],
                    [2, 8],
                    [1, 4],
                    [2, 2],
                    [1, 10],
                    [2, 10]
                ]
            ],
            "expected" => 1
        ],
        [
            "input" => [
                "L" => 100,
                "N" => 5,
                "selections" => [
                    [1, 100],
                    [1, 100],
                    [1, 100],
                    [1, 100],
                    [1, 100]
                ]
            ],
            "expected" => 100
        ]
    ];

    foreach ($tests as $index => $test) {
        $input = $test["input"];
        $expected = $test["expected"];
        $result = count_highlighted_letters($input["L"], $input["N"], $input["selections"]);
        echo "Test " . ($index + 1) . ": " . ($result === $expected ? "Passed" : "Failed") . "\n";
    }
}

// Run the tests
run_tests();