algorithm-neet-code-top-150-python-visual/visual/0190_reverse_bits.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>Reverse Bits - LeetCode 190</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">#0190</span> Reverse Bits</h1>
            <p><strong>Problem:</strong> Reverse bits of a given 32 bits unsigned integer.</p>
            <p><strong>Pattern:</strong> Bit Manipulation - Extract bits from right, build result from left</p>
            <div class="problem-meta">
                <span class="meta-tag">💻 Bit</span>
                <span class="meta-tag">⏱️ O(n)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0190_reverse_bits/0190_reverse_bits.py</code>
            </div>

        </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>A linked list is like a <strong>chain of train cars</strong>:</p>
            <ul>
                <li><strong>Each node:</strong> Contains data and points to next node</li>
                <li><strong>Traversal:</strong> Follow the chain one node at a time</li>
                <li><strong>Modification:</strong> Redirect links to rearrange</li>
                <li><strong>Two pointers:</strong> Often use slow/fast pointers</li>
            </ul>
        </div>


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

            <div class="visualization">
            <svg id="mainSvg"></svg>
        </div>

        <div class="controls">
            <button id="stepBtn">Step</button>
            <button id="autoBtn">Auto Run</button>
            <button id="resetBtn">Reset</button>
            <div class="speed-control">
                <label for="speed">Speed:</label>
                <input type="range" id="speed" min="100" max="2000" value="600">
            </div>
        </div>

        <div class="status" id="status">Click "Step" to reverse bits one at a time</div>

        <div class="variables">
            <div class="var-item">
                <span class="var-label">Bit Position:</span>
                <span id="bitPos">-</span>
            </div>
            <div class="var-item">
                <span class="var-label">Current Bit:</span>
                <span id="currentBit">-</span>
            </div>
        </div>

        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">reverseBits</span>(n):
    <span class="string">"""
    Reverse the bits of a 32-bit unsigned integer.
    Extract each bit from right, place it from left.
    Time: O(32) = O(1), Space: O(1)
    """</span>
    result = <span class="number">0</span>
    <span class="keyword">for</span> i <span class="keyword">in</span> <span class="function">range</span>(<span class="number">32</span>):
        bit = (n >> i) & <span class="number">1</span>  <span class="comment"># Get bit at position i</span>
        result |= bit << (<span class="number">31</span> - i)  <span class="comment"># Place at reversed position</span>
    <span class="keyword">return</span> result</pre>
            </div>
        </div>
    </div>

    <script>
        // Use 8 bits for visualization simplicity
        const BITS = 8;
        const originalNum = 43; // 00101011
        let n = originalNum;
        let result = 0;
        let bitPosition = 0;
        let autoRunning = false;
        let autoTimer = null;

        const width = 800;
        const height = 400;
        const svg = d3.select("#mainSvg")
            .attr("width", width)
            .attr("height", height);

        function toBinary(num, bits = BITS) {
            return (num >>> 0).toString(2).padStart(bits, '0');
        }

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

            const originalBits = toBinary(originalNum);
            const currentBits = toBinary(n);
            const resultBits = toBinary(result);

            // Title
            svg.append("text")
                .attr("x", width / 2)
                .attr("y", 30)
                .attr("text-anchor", "middle")
                .attr("font-weight", "bold")
                .text(`Reversing bits of ${originalNum} (${BITS}-bit demo)`);

            // Original number
            svg.append("text")
                .attr("x", 100)
                .attr("y", 80)
                .attr("text-anchor", "end")
                .attr("font-weight", "bold")
                .text("Original:");

            drawBitArray(originalBits, 120, 60, "original");

            // Arrow showing extraction
            if (bitPosition < BITS) {
                const extractX = 120 + (BITS - 1 - bitPosition) * 45 + 17;
                svg.append("path")
                    .attr("d", `M${extractX},100 L${extractX},130`)
                    .attr("stroke", "#f57c00")
                    .attr("stroke-width", 2)
                    .attr("marker-end", "url(#arrow)");

                svg.append("text")
                    .attr("x", extractX)
                    .attr("y", 150)
                    .attr("text-anchor", "middle")
                    .attr("fill", "#f57c00")
                    .attr("font-size", "12px")
                    .text(`Extract bit ${bitPosition}`);
            }

            // Current n (remaining)
            svg.append("text")
                .attr("x", 100)
                .attr("y", 200)
                .attr("text-anchor", "end")
                .text("n (shifted):");

            drawBitArray(currentBits, 120, 180, "current");

            // Result being built
            svg.append("text")
                .attr("x", 100)
                .attr("y", 300)
                .attr("text-anchor", "end")
                .attr("font-weight", "bold")
                .text("Result:");

            drawBitArray(resultBits, 120, 280, "result");

            // Arrow showing placement
            if (bitPosition > 0 && bitPosition <= BITS) {
                const placeX = 120 + (bitPosition - 1) * 45 + 17;
                svg.append("path")
                    .attr("d", `M${placeX},250 L${placeX},275`)
                    .attr("stroke", "#4caf50")
                    .attr("stroke-width", 2)
                    .attr("marker-end", "url(#arrow-green)");
            }

            // Values
            svg.append("text")
                .attr("x", 520)
                .attr("y", 80)
                .attr("font-size", "14px")
                .text(`= ${originalNum}`);

            svg.append("text")
                .attr("x", 520)
                .attr("y", 200)
                .attr("font-size", "14px")
                .text(`= ${n}`);

            svg.append("text")
                .attr("x", 520)
                .attr("y", 300)
                .attr("font-size", "14px")
                .attr("font-weight", "bold")
                .attr("fill", bitPosition === BITS ? "#4caf50" : "#333")
                .text(`= ${result}`);

            // Formula
            svg.append("text")
                .attr("x", width / 2)
                .attr("y", 360)
                .attr("text-anchor", "middle")
                .attr("font-family", "monospace")
                .attr("font-size", "14px")
                .text(bitPosition < BITS ?
                    `bit = (n >> ${bitPosition}) & 1 = ${(n >> bitPosition) & 1}, result |= bit << ${BITS - 1 - bitPosition}` :
                    `Complete! ${originalNum} reversed = ${result}`);

            // Define arrow markers
            svg.append("defs").html(`
                <marker id="arrow" markerWidth="10" markerHeight="10" refX="5" refY="5" orient="auto">
                    <path d="M0,0 L10,5 L0,10 Z" fill="#f57c00"/>
                </marker>
                <marker id="arrow-green" markerWidth="10" markerHeight="10" refX="5" refY="5" orient="auto">
                    <path d="M0,0 L10,5 L0,10 Z" fill="#4caf50"/>
                </marker>
            `);
        }

        function drawBitArray(bits, x, y, type) {
            const bitArray = bits.split('');

            bitArray.forEach((bit, i) => {
                const isHighlighted = type === "original" && i === BITS - 1 - bitPosition;
                const isPlaced = type === "result" && i < bitPosition;
                const isCurrent = type === "result" && i === bitPosition - 1;

                svg.append("rect")
                    .attr("x", x + i * 45)
                    .attr("y", y)
                    .attr("width", 35)
                    .attr("height", 35)
                    .attr("rx", 5)
                    .attr("fill", isHighlighted ? "#fff3e0" :
                                  isCurrent ? "#c8e6c9" :
                                  isPlaced ? "#e8f5e9" :
                                  bit === '1' ? "#e3f2fd" : "#f5f5f5")
                    .attr("stroke", isHighlighted ? "#f57c00" :
                                   isCurrent ? "#4caf50" :
                                   bit === '1' ? "#1976d2" : "#bdbdbd")
                    .attr("stroke-width", isHighlighted || isCurrent ? 3 : 2);

                svg.append("text")
                    .attr("x", x + i * 45 + 17.5)
                    .attr("y", y + 22)
                    .attr("text-anchor", "middle")
                    .attr("font-family", "monospace")
                    .attr("font-size", "18px")
                    .attr("font-weight", "bold")
                    .attr("fill", bit === '1' ? "#1976d2" : "#999")
                    .text(bit);
            });
        }

        function step() {
            if (bitPosition >= BITS) return false;

            const bit = (originalNum >> bitPosition) & 1;
            result |= bit << (BITS - 1 - bitPosition);
            n = originalNum >> (bitPosition + 1);

            document.getElementById("bitPos").textContent = bitPosition;
            document.getElementById("currentBit").textContent = bit;

            bitPosition++;
            draw();

            if (bitPosition >= BITS) {
                document.getElementById("status").textContent =
                    `Complete! ${originalNum} → ${result} (reversed)`;
                return false;
            } else {
                document.getElementById("status").textContent =
                    `Extracted bit ${bitPosition - 1} (value: ${bit}), placed at position ${BITS - bitPosition}`;
                return true;
            }
        }

        function reset() {
            n = originalNum;
            result = 0;
            bitPosition = 0;
            autoRunning = false;
            if (autoTimer) clearInterval(autoTimer);

            document.getElementById("bitPos").textContent = "-";
            document.getElementById("currentBit").textContent = "-";
            document.getElementById("status").textContent = 'Click "Step" to reverse bits one at a time';
            document.getElementById("autoBtn").textContent = "Auto Run";

            draw();
        }

        function autoRun() {
            if (autoRunning) {
                autoRunning = false;
                clearInterval(autoTimer);
                document.getElementById("autoBtn").textContent = "Auto Run";
            } else {
                autoRunning = true;
                document.getElementById("autoBtn").textContent = "Pause";
                const speed = 2100 - document.getElementById("speed").value;
                autoTimer = setInterval(() => {
                    if (!step()) {
                        autoRunning = false;
                        clearInterval(autoTimer);
                        document.getElementById("autoBtn").textContent = "Auto Run";
                    }
                }, speed);
            }
        }

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

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