algorithm-neet-code-top-150-python-visual/visual/0066_plus_one.html at main · kimtth/algorithm-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>066 - Plus One</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">#066</span> Plus One</h1>
            <p>
                Given a large integer represented as an integer array digits, increment one to the integer.
                Handle carry propagation when digit is 9. May need to prepend 1 for cases like 999 + 1 = 1000.
            </p>
            <div class="problem-meta">
                <span class="meta-tag">🔢 Math</span>
                <span class="meta-tag">⏱️ O(n)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0066_plus_one/0066_plus_one.py</code>
            </div>

        </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>This algorithm solves the problem <strong>step by step</strong>:</p>
            <ul>
                <li><strong>Understand:</strong> Parse the input data</li>
                <li><strong>Process:</strong> Apply the core logic</li>
                <li><strong>Optimize:</strong> Use efficient data structures</li>
                <li><strong>Return:</strong> Output the computed result</li>
            </ul>
        </div>


        <section class="visualization-section">
            <h3>🎬 Step-by-Step Visualization</h3>
            <div class="controls">
                <button id="autoRunBtn" class="btn">▶ Auto Run</button>
                <button id="stepBtn" class="btn btn-success">Step</button>
                <button id="resetBtn" class="btn btn-danger">Reset</button>
                <select id="exampleSelect" style="margin-left: 15px; padding: 8px;">
                    <option value="129">Example: [1, 2, 9]</option>
                    <option value="999">Example: [9, 9, 9]</option>
                    <option value="123">Example: [1, 2, 3]</option>
                </select>
            </div>
            <div class="status" id="status">Add 1 to the number</div>
            <svg id="visualization"></svg>
        </section>

        <section class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">plusOne</span>(digits):
    <span class="keyword">for</span> i <span class="keyword">in</span> <span class="function">range</span>(<span class="function">len</span>(digits) - <span class="number">1</span>, <span class="number">-1</span>, <span class="number">-1</span>):
        <span class="keyword">if</span> digits[i] < <span class="number">9</span>:
            digits[i] += <span class="number">1</span>
            <span class="keyword">return</span> digits
        digits[i] = <span class="number">0</span>

    <span class="comment"># All digits were 9</span>
    <span class="keyword">return</span> [<span class="number">1</span>] + digits</pre>
            </div>
        </section>
    </div>

    <script>
        const width = 900;
        const height = 450;

        const svg = d3.select("#visualization")
            .attr("width", width)
            .attr("height", height);

        let originalDigits = [1, 2, 9];
        let digits;
        let currentIdx;
        let phase = "init";
        let animationTimer = null;
        let carry = 1;

        document.getElementById("exampleSelect").addEventListener("change", (e) => {
            originalDigits = e.target.value.split('').map(Number);
            reset();
        });

        function reset() {
            digits = [...originalDigits];
            currentIdx = digits.length - 1;
            phase = "init";
            carry = 1;

            if (animationTimer) clearInterval(animationTimer);
            animationTimer = null;
            document.getElementById("autoRunBtn").textContent = "▶ Auto Run";
            document.getElementById("status").textContent = `Add 1 to [${originalDigits.join(', ')}]`;
            render();
        }

        function render() {
            svg.selectAll("*").remove();

            const cellWidth = 70;
            const startX = 100;
            const arrayY = 100;

            // Title
            svg.append("text")
                .attr("x", 30)
                .attr("y", 40)
                .attr("font-size", "14px")
                .attr("font-weight", "bold")
                .attr("fill", "#1e293b")
                .text(`Plus One: [${originalDigits.join(', ')}] + 1`);

            // Draw current digits
            svg.append("text")
                .attr("x", 30)
                .attr("y", arrayY + 30)
                .attr("font-size", "13px")
                .attr("fill", "#64748b")
                .text("digits:");

            digits.forEach((digit, idx) => {
                const x = startX + idx * cellWidth;
                const isCurrent = idx === currentIdx && phase !== "done";
                const isModified = idx > currentIdx || (idx === currentIdx && phase === "done");

                svg.append("rect")
                    .attr("x", x)
                    .attr("y", arrayY)
                    .attr("width", cellWidth - 10)
                    .attr("height", 55)
                    .attr("rx", 8)
                    .attr("fill", () => {
                        if (isCurrent) return "#fef3c7";
                        if (isModified) return "#d1fae5";
                        return "#f8fafc";
                    })
                    .attr("stroke", () => {
                        if (isCurrent) return "#f59e0b";
                        if (isModified) return "#10b981";
                        return "#94a3b8";
                    })
                    .attr("stroke-width", isCurrent ? 3 : 2);

                svg.append("text")
                    .attr("x", x + (cellWidth - 10) / 2)
                    .attr("y", arrayY + 38)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "24px")
                    .attr("font-weight", "bold")
                    .attr("fill", "#1e293b")
                    .text(digit);

                // Index label
                svg.append("text")
                    .attr("x", x + (cellWidth - 10) / 2)
                    .attr("y", arrayY + 75)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "11px")
                    .attr("fill", "#64748b")
                    .text(`[${idx}]`);

                // Current pointer
                if (isCurrent) {
                    svg.append("text")
                        .attr("x", x + (cellWidth - 10) / 2)
                        .attr("y", arrayY - 15)
                        .attr("text-anchor", "middle")
                        .attr("font-size", "12px")
                        .attr("font-weight", "bold")
                        .attr("fill", "#f59e0b")
                        .text("▼ checking");
                }
            });

            // Carry indicator
            if (carry && phase !== "done") {
                svg.append("rect")
                    .attr("x", startX + digits.length * cellWidth + 20)
                    .attr("y", arrayY)
                    .attr("width", 80)
                    .attr("height", 55)
                    .attr("rx", 8)
                    .attr("fill", "#fce7f3")
                    .attr("stroke", "#ec4899");

                svg.append("text")
                    .attr("x", startX + digits.length * cellWidth + 60)
                    .attr("y", arrayY + 25)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "12px")
                    .attr("fill", "#ec4899")
                    .text("carry");

                svg.append("text")
                    .attr("x", startX + digits.length * cellWidth + 60)
                    .attr("y", arrayY + 45)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "20px")
                    .attr("font-weight", "bold")
                    .attr("fill", "#1e293b")
                    .text("+1");
            }

            // Algorithm explanation
            const algoY = 230;
            svg.append("text")
                .attr("x", 30)
                .attr("y", algoY)
                .attr("font-size", "13px")
                .attr("font-weight", "bold")
                .attr("fill", "#1e293b")
                .text("Algorithm:");

            const steps = [
                "1. Start from rightmost digit",
                "2. If digit < 9: add 1 and return",
                "3. If digit = 9: set to 0, carry to left",
                "4. If all 9s: prepend 1 (e.g., 999 → 1000)"
            ];

            steps.forEach((step, i) => {
                svg.append("text")
                    .attr("x", 30)
                    .attr("y", algoY + 25 + i * 22)
                    .attr("font-size", "12px")
                    .attr("fill", "#64748b")
                    .text(step);
            });

            // Result
            if (phase === "done") {
                svg.append("rect")
                    .attr("x", 30)
                    .attr("y", 360)
                    .attr("width", 450)
                    .attr("height", 55)
                    .attr("rx", 10)
                    .attr("fill", "#d1fae5")
                    .attr("stroke", "#10b981")
                    .attr("stroke-width", 2);

                svg.append("text")
                    .attr("x", 255)
                    .attr("y", 395)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "18px")
                    .attr("font-weight", "bold")
                    .attr("fill", "#10b981")
                    .text(`✓ [${originalDigits.join(', ')}] + 1 = [${digits.join(', ')}]`);
            }
        }

        function step() {
            if (phase === "done") return;

            if (currentIdx < 0) {
                // Need to prepend 1
                digits.unshift(1);
                phase = "done";
                document.getElementById("status").textContent =
                    `All digits were 9! Prepending 1: [${digits.join(', ')}]`;
                render();
                return;
            }

            if (digits[currentIdx] < 9) {
                digits[currentIdx]++;
                carry = 0;
                phase = "done";
                document.getElementById("status").textContent =
                    `✓ digits[${currentIdx}] = ${digits[currentIdx]-1} + 1 = ${digits[currentIdx]}. Done!`;
            } else {
                digits[currentIdx] = 0;
                document.getElementById("status").textContent =
                    `digits[${currentIdx}] = 9, set to 0, carry to left`;
                currentIdx--;
            }

            render();
        }

        function autoRun() {
            if (animationTimer) {
                clearInterval(animationTimer);
                animationTimer = null;
                document.getElementById("autoRunBtn").textContent = "▶ Auto Run";
                return;
            }

            document.getElementById("autoRunBtn").textContent = "⏸ Pause";
            animationTimer = setInterval(() => {
                if (phase === "done") {
                    clearInterval(animationTimer);
                    animationTimer = null;
                    document.getElementById("autoRunBtn").textContent = "▶ Auto Run";
                    return;
                }
                step();
            }, 1000);
        }

        document.getElementById("autoRunBtn").addEventListener("click", autoRun);
        document.getElementById("stepBtn").addEventListener("click", step);
        document.getElementById("resetBtn").addEventListener("click", reset);

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