algorithm-neet-code-top-150-python-visual/visual/0323_number_of_connected_components.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>Number of Connected Components - LeetCode 323</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">#0323</span> Number of Connected Components</h1>
            <p><strong>Problem:</strong> Given n nodes and edges, find the number of connected components in an undirected graph.</p>
            <p><strong>Pattern:</strong> Union-Find - Count number of unique parents after all unions</p>
            <div class="problem-meta">
                <span class="meta-tag">🔗 Graph</span>
                <span class="meta-tag">⏱️ O(n)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0323_number_of_connected_components_in_an_undirected_graph/0323_number_of_connected_components_in_an_undirected_graph.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>


        <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="800">
            </div>
        </div>

        <div class="status" id="status">Click "Step" to count connected components</div>

        <div class="variables">
            <div class="var-item">
                <span class="var-label">Current Edge:</span>
                <span id="edgeDisplay">-</span>
            </div>
            <div class="var-item">
                <span class="var-label">Parent Array:</span>
                <span id="parentDisplay">[0, 1, 2, 3, 4]</span>
            </div>
            <div class="var-item">
                <span class="var-label">Components:</span>
                <span id="componentDisplay">5</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">countComponents</span>(n, edges):
    <span class="string">"""
    Union-Find with path compression.
    Time: O(E * α(N)), Space: O(N)
    """</span>
    parent = <span class="function">list</span>(<span class="function">range</span>(n))
    rank = [<span class="number">1</span>] * n

    <span class="keyword">def</span> <span class="function">find</span>(x):
        <span class="keyword">if</span> parent[x] != x:
            parent[x] = <span class="function">find</span>(parent[x])  <span class="comment"># Path compression</span>
        <span class="keyword">return</span> parent[x]

    <span class="keyword">def</span> <span class="function">union</span>(x, y):
        px, py = <span class="function">find</span>(x), <span class="function">find</span>(y)
        <span class="keyword">if</span> px == py:
            <span class="keyword">return</span> <span class="number">0</span>  <span class="comment"># Already connected</span>
        <span class="keyword">if</span> rank[px] < rank[py]:
            px, py = py, px
        parent[py] = px
        rank[px] += rank[py]
        <span class="keyword">return</span> <span class="number">1</span>  <span class="comment"># Merged two components</span>

    components = n
    <span class="keyword">for</span> x, y <span class="keyword">in</span> edges:
        components -= <span class="function">union</span>(x, y)

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

    <script>
        const n = 5;
        const edges = [[0, 1], [1, 2], [3, 4]];
        // Result: 2 components {0,1,2} and {3,4}

        let parent = [];
        let rank = [];
        let edgeIndex = 0;
        let components = n;
        let nodeColors = {};
        let autoRunning = false;
        let autoTimer = null;

        const width = 700;
        const height = 380;
        const svg = d3.select("#mainSvg")
            .attr("width", width)
            .attr("height", height);

        const positions = [
            {x: 150, y: 120},  // Node 0
            {x: 280, y: 80},   // Node 1
            {x: 410, y: 120},  // Node 2
            {x: 500, y: 250},  // Node 3
            {x: 630, y: 210}   // Node 4
        ];

        const colorPalette = ["#e3f2fd", "#c8e6c9", "#fff3e0", "#f3e5f5", "#ffcdd2"];
        const strokePalette = ["#1976d2", "#4caf50", "#ff9800", "#7b1fa2", "#e53935"];

        function init() {
            parent = Array.from({length: n}, (_, i) => i);
            rank = new Array(n).fill(1);
            edgeIndex = 0;
            components = n;

            for (let i = 0; i < n; i++) {
                nodeColors[i] = i;
            }
        }

        function find(x) {
            if (parent[x] !== x) {
                parent[x] = find(parent[x]);
            }
            return parent[x];
        }

        function union(x, y) {
            const px = find(x);
            const py = find(y);

            if (px === py) return false;

            if (rank[px] < rank[py]) {
                parent[px] = py;
                // Update colors
                for (let i = 0; i < n; i++) {
                    if (find(i) === py) nodeColors[i] = py;
                }
            } else {
                parent[py] = px;
                for (let i = 0; i < n; i++) {
                    if (find(i) === px) nodeColors[i] = px;
                }
                if (rank[px] === rank[py]) rank[px]++;
            }

            return true;
        }

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

            svg.append("text")
                .attr("x", width / 2).attr("y", 25)
                .attr("text-anchor", "middle")
                .attr("font-weight", "bold")
                .text("Union-Find: Counting Connected Components");

            // Draw all edges
            edges.forEach(([u, v], i) => {
                const from = positions[u];
                const to = positions[v];

                const processed = i < edgeIndex;

                svg.append("line")
                    .attr("x1", from.x).attr("y1", from.y)
                    .attr("x2", to.x).attr("y2", to.y)
                    .attr("stroke", processed ? "#4caf50" : "#ddd")
                    .attr("stroke-width", processed ? 3 : 2)
                    .attr("stroke-dasharray", processed ? "none" : "5,5");
            });

            // Draw nodes
            for (let i = 0; i < n; i++) {
                const pos = positions[i];
                const colorIdx = nodeColors[i] % colorPalette.length;

                svg.append("circle")
                    .attr("cx", pos.x).attr("cy", pos.y).attr("r", 28)
                    .attr("fill", colorPalette[colorIdx])
                    .attr("stroke", strokePalette[colorIdx])
                    .attr("stroke-width", 2);

                svg.append("text")
                    .attr("x", pos.x).attr("y", pos.y + 6)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "18px")
                    .attr("font-weight", "bold")
                    .text(i);

                // Parent label
                svg.append("text")
                    .attr("x", pos.x).attr("y", pos.y + 45)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "11px")
                    .attr("fill", "#666")
                    .text(`p[${i}]=${parent[i]}`);
            }

            // Component count box
            svg.append("rect")
                .attr("x", width / 2 - 80).attr("y", height - 80)
                .attr("width", 160).attr("height", 45)
                .attr("rx", 10)
                .attr("fill", "#e8eaf6").attr("stroke", "#3f51b5");

            svg.append("text")
                .attr("x", width / 2).attr("y", height - 50)
                .attr("text-anchor", "middle")
                .attr("font-size", "18px")
                .attr("font-weight", "bold")
                .text(`Components: ${components}`);

            // Edge list
            svg.append("text")
                .attr("x", 30).attr("y", 280)
                .attr("font-weight", "bold")
                .text("Edges:");

            edges.forEach(([u, v], i) => {
                const processed = i < edgeIndex;
                const isCurrent = i === edgeIndex - 1;

                svg.append("rect")
                    .attr("x", 30).attr("y", 290 + i * 28)
                    .attr("width", 70).attr("height", 24)
                    .attr("rx", 4)
                    .attr("fill", processed ? "#c8e6c9" : "#f5f5f5")
                    .attr("stroke", isCurrent ? "#ff9800" : "#ddd")
                    .attr("stroke-width", isCurrent ? 2 : 1);

                svg.append("text")
                    .attr("x", 65).attr("y", 307 + i * 28)
                    .attr("text-anchor", "middle")
                    .attr("font-size", "12px")
                    .text(`(${u}, ${v})`);
            });
        }

        function step() {
            if (edgeIndex >= edges.length) {
                document.getElementById("status").textContent =
                    `Done! Found ${components} connected component${components !== 1 ? 's' : ''}`;
                draw();
                return false;
            }

            const [u, v] = edges[edgeIndex];
            document.getElementById("edgeDisplay").textContent = `(${u}, ${v})`;

            const merged = union(u, v);

            if (merged) {
                components--;
                document.getElementById("status").textContent =
                    `Union(${u}, ${v}): Merged! Components = ${components}`;
            } else {
                document.getElementById("status").textContent =
                    `Union(${u}, ${v}): Already connected. Components = ${components}`;
            }

            edgeIndex++;

            document.getElementById("parentDisplay").textContent =
                `[${parent.join(', ')}]`;
            document.getElementById("componentDisplay").textContent = components;

            draw();
            return edgeIndex < edges.length;
        }

        function reset() {
            init();
            autoRunning = false;
            if (autoTimer) clearInterval(autoTimer);

            document.getElementById("edgeDisplay").textContent = "-";
            document.getElementById("parentDisplay").textContent =
                `[${parent.join(', ')}]`;
            document.getElementById("componentDisplay").textContent = n;
            document.getElementById("status").textContent =
                'Click "Step" to count connected components';
            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);

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