neet-code-top-150-python-visual/visual/0007_reverse_integer.html at main · kimtth/neet-code-top-150-python-visual · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>LC 7: Reverse Integer - Algorithm Visualization</title>
    <link rel="stylesheet" href="styles.css">
    <script src="https://d3js.org/d3.v7.min.js"></script>
</head>
<body>
    <div class="container">
        <div class="problem-info">
            <h1><span class="problem-number">#7</span> Reverse Integer</h1>
            <p>Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-2³¹, 2³¹ - 1], return 0.</p>
            <div class="problem-meta">
                <span class="meta-tag">🔢 Math</span>
                <span class="meta-tag">📊 Modulo</span>
                <span class="meta-tag">⏱️ O(log n)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0007_reverse_integer/0007_reverse_integer.py</code>
            </div>
            </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>Reversing a number is like <strong>moving digits one by one</strong> from the end to build a new number:</p>
            <ul>
                <li><strong>Pop last digit:</strong> Use <code>x % 10</code> to get the last digit</li>
                <li><strong>Remove last digit:</strong> Use <code>x // 10</code> to shrink the number</li>
                <li><strong>Push to result:</strong> Use <code>result * 10 + digit</code> to build reversed number</li>
                <li><strong>Check overflow:</strong> Ensure result stays within 32-bit range</li>
            </ul>
        </div>


        <div class="visualization-section">
            <h3>🎬 Step-by-Step Visualization</h3>

            <div class="controls">
                <input type="number" id="numberInput" value="12345" style="width: 120px; padding: 10px; border-radius: 8px; border: 2px solid #ddd;">
                <button class="btn btn-primary" onclick="setNumber()">Set Number</button>
                <button class="btn btn-primary" id="stepBtn" onclick="step()">Step</button>
                <button class="btn btn-success" id="autoBtn" onclick="toggleAuto()">Auto Run</button>
                <button class="btn btn-warning" onclick="reset()">Reset</button>
            </div>

            <div class="status-message" id="statusMessage">
                Enter a number and click Step to begin
            </div>

            <div style="display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 20px 0;">
                <div class="array-section">
                    <div class="array-label">📥 Original Number</div>
                    <div id="originalViz" class="array-container" style="justify-content: center; padding: 20px; background: #f5f5f5; border-radius: 12px; min-height: 100px;"></div>
                </div>
                <div class="array-section">
                    <div class="array-label">📤 Reversed Number</div>
                    <div id="resultViz" class="array-container" style="justify-content: center; padding: 20px; background: #e8f5e9; border-radius: 12px; min-height: 100px;"></div>
                </div>
            </div>

            <div class="array-section">
                <div class="array-label">⚙️ Current Operation</div>
                <div id="operationArea" style="padding: 20px; background: #f5f5f5; border-radius: 12px; text-align: center; font-family: monospace; font-size: 1.1em;">
                    Click Step or Auto Run to begin
                </div>
            </div>
        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">reverse</span>(x: <span class="class-name">int</span>) -> <span class="class-name">int</span>:
    INT_MIN, INT_MAX = -<span class="number">2</span>**<span class="number">31</span>, <span class="number">2</span>**<span class="number">31</span> - <span class="number">1</span>

    result = <span class="number">0</span>
    sign = <span class="number">1</span> <span class="keyword">if</span> x >= <span class="number">0</span> <span class="keyword">else</span> -<span class="number">1</span>
    x = <span class="function">abs</span>(x)

    <span class="keyword">while</span> x != <span class="number">0</span>:
        digit = x % <span class="number">10</span>      <span class="comment"># Pop last digit</span>
        x //= <span class="number">10</span>            <span class="comment"># Remove last digit</span>

        <span class="comment"># Check for overflow before adding</span>
        <span class="keyword">if</span> result > (INT_MAX - digit) // <span class="number">10</span>:
            <span class="keyword">return</span> <span class="number">0</span>

        result = result * <span class="number">10</span> + digit  <span class="comment"># Push digit</span>

    <span class="keyword">return</span> sign * result</pre>
            </div>
        </div>
    </div>

    <script>
        const INT_MAX = 2147483647;
        const INT_MIN = -2147483648;

        let originalNumber = 12345;
        let x = 0;
        let result = 0;
        let sign = 1;
        let steps = [];
        let stepIndex = 0;
        let autoInterval = null;
        let isComplete = false;

        function setNumber() {
            const input = parseInt(document.getElementById('numberInput').value);
            if (!isNaN(input)) {
                originalNumber = input;
                reset();
            }
        }

        function reset() {
            sign = originalNumber >= 0 ? 1 : -1;
            x = Math.abs(originalNumber);
            result = 0;
            steps = [];
            stepIndex = 0;
            isComplete = false;

            if (autoInterval) {
                clearInterval(autoInterval);
                autoInterval = null;
                document.getElementById('autoBtn').textContent = 'Auto Run';
            }

            // Build all steps
            let tempX = x;
            let tempResult = 0;
            while (tempX !== 0) {
                const digit = tempX % 10;
                const newX = Math.floor(tempX / 10);
                const newResult = tempResult * 10 + digit;

                steps.push({
                    x: tempX,
                    digit: digit,
                    newX: newX,
                    result: tempResult,
                    newResult: newResult,
                    overflow: Math.abs(newResult) > INT_MAX
                });

                tempX = newX;
                tempResult = newResult;
            }

            render();
            document.getElementById('statusMessage').textContent = 'Enter a number and click Step to begin';
        }

        function step() {
            if (isComplete || stepIndex >= steps.length) {
                isComplete = true;
                render();
                return;
            }

            stepIndex++;
            render();
        }

        function toggleAuto() {
            if (autoInterval) {
                clearInterval(autoInterval);
                autoInterval = null;
                document.getElementById('autoBtn').textContent = 'Auto Run';
            } else {
                autoInterval = setInterval(() => {
                    if (stepIndex >= steps.length) {
                        clearInterval(autoInterval);
                        autoInterval = null;
                        document.getElementById('autoBtn').textContent = 'Auto Run';
                        isComplete = true;
                        render();
                    } else {
                        step();
                    }
                }, 1000);
                document.getElementById('autoBtn').textContent = 'Pause';
            }
        }

        function render() {
            const originalViz = document.getElementById('originalViz');
            const resultViz = document.getElementById('resultViz');
            const operationArea = document.getElementById('operationArea');

            const originalDigits = Math.abs(originalNumber).toString().split('');
            const processedCount = stepIndex;

            // Render original number
            let originalHtml = '';
            if (sign < 0) {
                originalHtml += '<div class="array-box" style="background: #ffcdd2; border-color: #f44336; width: 50px;">−</div>';
            }

            originalDigits.forEach((d, i) => {
                const revIndex = originalDigits.length - 1 - i;
                let style = '';
                if (revIndex < processedCount) {
                    style = 'background: #c8e6c9; border-color: #4caf50;';
                } else if (revIndex === processedCount && stepIndex > 0) {
                    style = 'background: #fff9c4; border-color: #fbc02d; transform: scale(1.1);';
                }
                originalHtml += `<div class="array-box" style="${style}">${d}</div>`;
            });
            originalViz.innerHTML = originalHtml;

            // Render result number
            let currentResult = 0;
            if (stepIndex > 0) {
                currentResult = steps[stepIndex - 1].newResult;
            }

            const resultStr = currentResult.toString();
            let resultHtml = '';
            if (sign < 0 && currentResult > 0) {
                resultHtml += '<div class="array-box" style="background: #ffcdd2; border-color: #f44336; width: 50px;">−</div>';
            }

            if (currentResult === 0 && stepIndex === 0) {
                resultHtml += '<div class="array-box" style="opacity: 0.5;">0</div>';
            } else {
                resultStr.split('').forEach((d) => {
                    resultHtml += `<div class="array-box" style="background: #c8e6c9; border-color: #4caf50;">${d}</div>`;
                });
            }
            resultViz.innerHTML = resultHtml;

            // Render operation
            if (stepIndex > 0 && stepIndex <= steps.length) {
                const s = steps[stepIndex - 1];
                operationArea.innerHTML = `
                    <div style="display: flex; justify-content: center; gap: 20px; flex-wrap: wrap;">
                        <span style="padding: 10px 15px; background: #e3f2fd; border-radius: 8px;">digit = ${s.x} % 10 = <strong>${s.digit}</strong></span>
                        <span style="padding: 10px 15px; background: #f5f5f5; border-radius: 8px;">x = ${s.x} / 10 = ${s.newX}</span>
                        <span style="padding: 10px 15px; background: #e8f5e9; border-radius: 8px;">result = ${s.result} × 10 + ${s.digit} = <strong>${s.newResult}</strong></span>
                    </div>
                    ${s.overflow ? '<div style="margin-top: 15px; padding: 10px; background: #ffebee; border-radius: 8px; color: #c62828;">⚠️ Overflow detected! Would return 0</div>' : ''}
                `;
                document.getElementById('statusMessage').textContent = `Step ${stepIndex}: Pop digit ${s.digit}, result = ${s.newResult}`;
            } else if (isComplete) {
                const finalResult = sign * (steps.length > 0 ? steps[steps.length - 1].newResult : 0);
                const overflow = Math.abs(finalResult) > INT_MAX;
                operationArea.innerHTML = `
                    <div style="font-size: 1.4em; color: #4caf50; font-weight: bold;">
                        Final Result: ${overflow ? 0 : finalResult}
                    </div>
                    ${overflow ? '<div style="margin-top: 15px; padding: 10px; background: #ffebee; border-radius: 8px; color: #c62828;">⚠️ Overflow! Return 0</div>' : ''}
                `;
                document.getElementById('statusMessage').className = 'status-message success';
                document.getElementById('statusMessage').textContent = `✅ Complete! Reversed: ${overflow ? 0 : finalResult}`;
            } else {
                operationArea.innerHTML = 'Click Step or Auto Run to begin';
            }
        }

        reset();
    </script>
</body>
</html>