algorithm-neet-code-top-150-python-visual/visual/0198_house_robber.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>LC 198: House Robber - 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">#198</span> House Robber</h1>
            <p>You are a robber planning to rob houses along a street. Adjacent houses have connected security systems - if you rob two adjacent houses, the police will be alerted. What's the maximum amount you can rob?</p>
            <div class="problem-meta">
                <span class="meta-tag">📈 Dynamic Programming</span>
                <span class="meta-tag">🏠 Array</span>
                <span class="meta-tag">⏱️ O(n)</span>
                <span class="meta-tag">💾 O(1)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0198_house_robber/0198_house_robber.py</code>
            </div>
            </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>At each house, you have a choice: <strong>rob it</strong> or <strong>skip it</strong>.</p>
            <ul>
                <li><strong>If you rob this house:</strong> You get its money + whatever you made from 2 houses back (you must skip the previous house)</li>
                <li><strong>If you skip this house:</strong> You keep whatever you made from the previous house</li>
                <li><strong>Decision:</strong> Pick whichever option gives you more money!</li>
                <li><strong>Key insight:</strong> We only need to track 2 values (not the entire history)</li>
            </ul>
        </div>


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

            <div class="controls">
                <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="info-box secondary" style="margin-bottom: 20px;">
                🏠 Houses with money: <strong>[2, 7, 9, 3, 1]</strong>
            </div>

            <div class="status-message" id="statusMessage">
                Click "Step" or "Auto Run" to start visualization
            </div>

            <div class="array-section">
                <div class="array-label">🏠 Houses (money in each):</div>
                <div class="array-container" id="housesContainer"></div>
            </div>

            <div class="variable-section" style="margin: 20px 0; display: flex; gap: 30px; justify-content: center;">
                <div class="variable">
                    <span class="var-name">rob1</span>
                    <span class="var-value" id="rob1Value">0</span>
                    <span class="var-desc">(max from 2 back)</span>
                </div>
                <div class="variable">
                    <span class="var-name">rob2</span>
                    <span class="var-value" id="rob2Value">0</span>
                    <span class="var-desc">(max from prev)</span>
                </div>
                <div class="variable">
                    <span class="var-name">temp</span>
                    <span class="var-value" id="tempValue">-</span>
                    <span class="var-desc">(new best)</span>
                </div>
            </div>

            <div class="explanation-panel" style="margin-top: 20px;">
                <h4>📝 Decision at Each House</h4>
                <div id="decisionDisplay" style="font-size: 1.1em; padding: 10px;">
                    Waiting to start...
                </div>
            </div>

            <div id="chartContainer" style="width: 100%; height: 250px; margin-top: 20px;"></div>
        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">rob</span>(self, nums: <span class="class-name">list</span>[<span class="class-name">int</span>]) -> <span class="class-name">int</span>:
    <span class="keyword">if</span> <span class="keyword">not</span> nums:
        <span class="keyword">return</span> <span class="number">0</span>
    <span class="keyword">if</span> <span class="function">len</span>(nums) == <span class="number">1</span>:
        <span class="keyword">return</span> nums[<span class="number">0</span>]

    rob1 = <span class="number">0</span>  <span class="comment"># max money up to i-2</span>
    rob2 = <span class="number">0</span>  <span class="comment"># max money up to i-1</span>

    <span class="keyword">for</span> num <span class="keyword">in</span> nums:
        temp = <span class="function">max</span>(rob1 + num, rob2)
        rob1 = rob2
        rob2 = temp

    <span class="keyword">return</span> rob2</pre>
            </div>
        </div>
    </div>

    <script>
        const houses = [2, 7, 9, 3, 1];
        let rob1 = 0;
        let rob2 = 0;
        let currentIndex = -1;
        let autoInterval = null;
        let history = [{rob1: 0, rob2: 0}];
        let decisions = [];

        function init() {
            renderHouses();
            renderChart();
        }

        function renderHouses() {
            const container = document.getElementById('housesContainer');
            container.innerHTML = '';

            houses.forEach((value, i) => {
                const box = document.createElement('div');
                box.className = 'array-box';
                box.id = `house-${i}`;
                box.innerHTML = `$${value}<span class="index-label">🏠 ${i}</span>`;
                box.style.background = '#f5f5f5';

                if (i < currentIndex) {
                    const robbed = decisions[i];
                    box.style.background = robbed ? '#c8e6c9' : '#ffcdd2';
                    box.style.borderColor = robbed ? '#4caf50' : '#f44336';
                }
                if (i === currentIndex) {
                    box.classList.add('highlight');
                }

                container.appendChild(box);
            });
        }

        function renderChart() {
            d3.select('#chartContainer').selectAll('*').remove();

            const margin = {top: 20, right: 30, bottom: 40, left: 50};
            const width = document.getElementById('chartContainer').offsetWidth - margin.left - margin.right;
            const height = 200 - margin.top - margin.bottom;

            const svg = d3.select('#chartContainer')
                .append('svg')
                .attr('width', width + margin.left + margin.right)
                .attr('height', height + margin.top + margin.bottom)
                .append('g')
                .attr('transform', `translate(${margin.left},${margin.top})`);

            const maxVal = Math.max(12, d3.max(history, d => Math.max(d.rob1, d.rob2)));

            const xScale = d3.scaleLinear()
                .domain([0, Math.max(houses.length, history.length - 1)])
                .range([0, width]);

            const yScale = d3.scaleLinear()
                .domain([0, maxVal])
                .range([height, 0]);

            // X axis
            svg.append('g')
                .attr('transform', `translate(0,${height})`)
                .call(d3.axisBottom(xScale).ticks(houses.length));

            // Y axis
            svg.append('g')
                .call(d3.axisLeft(yScale));

            // Labels
            svg.append('text')
                .attr('x', width / 2)
                .attr('y', height + 35)
                .attr('text-anchor', 'middle')
                .text('House Index');

            // rob2 line (current max)
            const rob2Line = d3.line()
                .x((d, i) => xScale(i))
                .y(d => yScale(d.rob2));

            svg.append('path')
                .datum(history)
                .attr('fill', 'none')
                .attr('stroke', '#4caf50')
                .attr('stroke-width', 3)
                .attr('d', rob2Line);

            // rob1 line (previous max)
            const rob1Line = d3.line()
                .x((d, i) => xScale(i))
                .y(d => yScale(d.rob1));

            svg.append('path')
                .datum(history)
                .attr('fill', 'none')
                .attr('stroke', '#2196f3')
                .attr('stroke-width', 2)
                .attr('stroke-dasharray', '5,5')
                .attr('d', rob1Line);

            // Legend
            svg.append('circle').attr('cx', width - 100).attr('cy', 10).attr('r', 6).style('fill', '#4caf50');
            svg.append('text').attr('x', width - 90).attr('y', 10).text('rob2 (current max)').style('font-size', '12px').attr('alignment-baseline', 'middle');
            svg.append('circle').attr('cx', width - 100).attr('cy', 30).attr('r', 6).style('fill', '#2196f3');
            svg.append('text').attr('x', width - 90).attr('y', 30).text('rob1 (2 back)').style('font-size', '12px').attr('alignment-baseline', 'middle');
        }

        function step() {
            currentIndex++;

            if (currentIndex >= houses.length) {
                document.getElementById('statusMessage').className = 'status-message success';
                document.getElementById('statusMessage').textContent =
                    `✅ Done! Maximum money that can be robbed: $${rob2}`;
                document.getElementById('stepBtn').disabled = true;
                stopAuto();
                return;
            }

            const num = houses[currentIndex];
            const option1 = rob1 + num;  // rob this house
            const option2 = rob2;         // skip this house
            const temp = Math.max(option1, option2);
            const robbed = option1 > option2;

            decisions.push(robbed);

            document.getElementById('statusMessage').textContent =
                `House ${currentIndex}: Rob ($${rob1} + $${num} = $${option1}) vs Skip ($${rob2})`;

            document.getElementById('decisionDisplay').innerHTML =
                `<strong>At House ${currentIndex} ($${num}):</strong><br>` +
                `Option 1 (Rob): $${rob1} + $${num} = $${option1}<br>` +
                `Option 2 (Skip): keep $${rob2}<br>` +
                `<strong>Decision: ${robbed ? '✅ ROB' : '❌ SKIP'} → Max = $${temp}</strong>`;

            document.getElementById('tempValue').textContent = temp;

            // Update for next iteration
            rob1 = rob2;
            rob2 = temp;

            document.getElementById('rob1Value').textContent = rob1;
            document.getElementById('rob2Value').textContent = rob2;

            history.push({rob1, rob2});

            renderHouses();
            renderChart();
        }

        function toggleAuto() {
            if (autoInterval) {
                stopAuto();
            } else {
                document.getElementById('autoBtn').textContent = 'Pause';
                autoInterval = setInterval(() => {
                    if (currentIndex >= houses.length - 1) {
                        step();
                        stopAuto();
                    } else {
                        step();
                    }
                }, 1500);
            }
        }

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

        function reset() {
            stopAuto();
            rob1 = 0;
            rob2 = 0;
            currentIndex = -1;
            history = [{rob1: 0, rob2: 0}];
            decisions = [];
            document.getElementById('stepBtn').disabled = false;
            document.getElementById('statusMessage').className = 'status-message';
            document.getElementById('statusMessage').textContent = 'Click "Step" or "Auto Run" to start visualization';
            document.getElementById('rob1Value').textContent = '0';
            document.getElementById('rob2Value').textContent = '0';
            document.getElementById('tempValue').textContent = '-';
            document.getElementById('decisionDisplay').textContent = 'Waiting to start...';
            init();
        }

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