algorithm-neet-code-top-150-python-visual/visual/0101_symmetric_tree.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>Symmetric Tree - LeetCode 101</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">#101</span> Symmetric Tree</h1>
            <p>Check whether a binary tree is a mirror of itself (symmetric around its center).</p>
            <div class="problem-meta">
                <span class="meta-tag">Tree</span>
                <span class="meta-tag">BFS/DFS</span>
                <span class="meta-tag">Easy</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/0101_symmetric_tree/0101_symmetric_tree.py</code>
            </div>

        </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>Tree traversal is like <strong>exploring a family tree</strong>:</p>
            <ul>
                <li><strong>Root:</strong> Start at the top node</li>
                <li><strong>Recurse:</strong> Visit left and right children</li>
                <li><strong>Base case:</strong> Stop at null/leaf nodes</li>
                <li><strong>Combine:</strong> Build answer from subtree results</li>
            </ul>
        </div>


        <div class="visualization-section">
            <h3>🎬 Step-by-Step Visualization</h3>
            <div class="controls">
                <button id="stepBtn">Step</button>
                <button id="autoBtn">Auto Run</button>
                <button id="resetBtn">Reset</button>
            </div>
            <svg id="mainSvg" width="700" height="380"></svg>
            <div class="status-message" id="status">Click "Step" to check symmetry</div>
        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">isSymmetric</span>(root):
    <span class="keyword">def</span> <span class="function">isMirror</span>(left, right):
        <span class="keyword">if</span> <span class="keyword">not</span> left <span class="keyword">and</span> <span class="keyword">not</span> right:
            <span class="keyword">return</span> <span class="keyword">True</span>
        <span class="keyword">if</span> <span class="keyword">not</span> left <span class="keyword">or</span> <span class="keyword">not</span> right:
            <span class="keyword">return</span> <span class="keyword">False</span>
        <span class="keyword">return</span> (left.val == right.val <span class="keyword">and</span>
                <span class="function">isMirror</span>(left.left, right.right) <span class="keyword">and</span>
                <span class="function">isMirror</span>(left.right, right.left))

    <span class="keyword">return</span> <span class="function">isMirror</span>(root.left, root.right)</pre>
            </div>
        </div>
    </div>

    <script>
        const tree = {
            val: 1,
            left: { val: 2, left: { val: 3, left: null, right: null }, right: { val: 4, left: null, right: null } },
            right: { val: 2, left: { val: 4, left: null, right: null }, right: { val: 3, left: null, right: null } }
        };

        let comparisons = [];
        let currentPair = null;
        let result = null;
        let stepIdx = 0;

        const width = 700, height = 380;
        const svg = d3.select("#mainSvg");
        let autoTimer = null, autoRunning = false;

        function generateComparisons(left, right, leftPath, rightPath) {
            const pairs = [];
            function helper(l, r, lp, rp) {
                pairs.push({ left: l, right: r, leftPath: lp, rightPath: rp });
                if (l && r) {
                    helper(l.left, r.right, lp + 'L', rp + 'R');
                    helper(l.right, r.left, lp + 'R', rp + 'L');
                }
            }
            helper(left, right, leftPath, rightPath);
            return pairs;
        }

        function drawTree(node, x, y, dx, path, highlightPath) {
            if (!node) return;
            const r = 22;

            if (node.left) {
                svg.append("line").attr("x1", x).attr("y1", y + r)
                    .attr("x2", x - dx).attr("y2", y + 55 - r)
                    .attr("stroke", "#ccc").attr("stroke-width", 2);
                drawTree(node.left, x - dx, y + 55, dx / 2, path + 'L', highlightPath);
            }
            if (node.right) {
                svg.append("line").attr("x1", x).attr("y1", y + r)
                    .attr("x2", x + dx).attr("y2", y + 55 - r)
                    .attr("stroke", "#ccc").attr("stroke-width", 2);
                drawTree(node.right, x + dx, y + 55, dx / 2, path + 'R', highlightPath);
            }

            let fill = "#e3f2fd", stroke = "#1976d2";
            if (highlightPath && highlightPath.includes(path)) {
                fill = "#fef3c7"; stroke = "#f59e0b";
            }

            svg.append("circle").attr("cx", x).attr("cy", y).attr("r", r)
                .attr("fill", fill).attr("stroke", stroke).attr("stroke-width", 2);
            svg.append("text").attr("x", x).attr("y", y + 6)
                .attr("text-anchor", "middle").attr("font-size", "16px")
                .attr("font-weight", "bold").text(node.val);
        }

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

            svg.append("text").attr("x", width/2).attr("y", 25)
                .attr("text-anchor", "middle").attr("font-weight", "bold")
                .text("Is This Tree Symmetric?");

            // Draw mirror line
            svg.append("line").attr("x1", width/2).attr("y1", 50)
                .attr("x2", width/2).attr("y2", 250)
                .attr("stroke", "#e91e63").attr("stroke-width", 2)
                .attr("stroke-dasharray", "5,5");

            svg.append("text").attr("x", width/2).attr("y", 265)
                .attr("text-anchor", "middle").attr("font-size", "11px")
                .attr("fill", "#e91e63").text("Mirror Line");

            const highlights = currentPair ? [currentPair.leftPath, currentPair.rightPath] : [];
            drawTree(tree, width/2, 70, 120, 'root', highlights);

            // Current comparison
            if (currentPair) {
                const lVal = currentPair.left ? currentPair.left.val : "null";
                const rVal = currentPair.right ? currentPair.right.val : "null";
                const match = (!currentPair.left && !currentPair.right) ||
                    (currentPair.left && currentPair.right && currentPair.left.val === currentPair.right.val);

                svg.append("rect").attr("x", width/2 - 150).attr("y", 290)
                    .attr("width", 300).attr("height", 40).attr("rx", 10)
                    .attr("fill", match ? "#d1fae5" : "#fee2e2")
                    .attr("stroke", match ? "#10b981" : "#ef4444");

                svg.append("text").attr("x", width/2).attr("y", 316)
                    .attr("text-anchor", "middle").attr("font-size", "14px")
                    .text(`Comparing: ${lVal} ↔ ${rVal} ${match ? "✓ Match" : "✗ Mismatch"}`);
            }

            // Result
            if (result !== null) {
                svg.append("rect").attr("x", width/2 - 100).attr("y", 340)
                    .attr("width", 200).attr("height", 35).attr("rx", 10)
                    .attr("fill", result ? "#d1fae5" : "#fee2e2")
                    .attr("stroke", result ? "#10b981" : "#ef4444");
                svg.append("text").attr("x", width/2).attr("y", 363)
                    .attr("text-anchor", "middle").attr("font-weight", "bold")
                    .attr("fill", result ? "#10b981" : "#ef4444")
                    .text(result ? "✓ Symmetric!" : "✗ Not Symmetric");
            }
        }

        function step() {
            if (result !== null) return false;

            if (stepIdx >= comparisons.length) {
                result = true;
                document.getElementById("status").textContent = "All pairs match! Tree is symmetric.";
                draw();
                return false;
            }

            currentPair = comparisons[stepIdx];
            const lVal = currentPair.left ? currentPair.left.val : "null";
            const rVal = currentPair.right ? currentPair.right.val : "null";

            const match = (!currentPair.left && !currentPair.right) ||
                (currentPair.left && currentPair.right && currentPair.left.val === currentPair.right.val);

            if (!match) {
                result = false;
                document.getElementById("status").textContent = `${lVal} ≠ ${rVal}. Not symmetric!`;
            } else {
                document.getElementById("status").textContent = `${lVal} = ${rVal}. Continue checking...`;
                stepIdx++;
            }

            draw();
            return result === null;
        }

        function reset() {
            comparisons = generateComparisons(tree.left, tree.right, 'rootL', 'rootR');
            currentPair = null; result = null; stepIdx = 0;
            if (autoTimer) clearInterval(autoTimer);
            autoRunning = false;
            document.getElementById("autoBtn").textContent = "Auto Run";
            document.getElementById("status").textContent = 'Click "Step" to check symmetry';
            draw();
        }

        function autoRun() {
            if (autoRunning) { clearInterval(autoTimer); autoRunning = false; document.getElementById("autoBtn").textContent = "Auto Run"; }
            else {
                autoRunning = true; document.getElementById("autoBtn").textContent = "Pause";
                autoTimer = setInterval(() => { if (!step()) { clearInterval(autoTimer); autoRunning = false; document.getElementById("autoBtn").textContent = "Auto Run"; } }, 800);
            }
        }

        document.getElementById("stepBtn").addEventListener("click", step);
        document.getElementById("autoBtn").addEventListener("click", autoRun);
        document.getElementById("resetBtn").addEventListener("click", reset);
        reset();
    </script>
</body>
</html>