212 lines
8.0 KiB
HTML
212 lines
8.0 KiB
HTML
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<!DOCTYPE html>
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<html lang="zh-Hans">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>049. 二叉树的最近公共祖先 – 图解</title>
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<link rel="stylesheet" href="../shared/style.css">
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<style>
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/* page-specific overrides */
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.vis-area { min-height: 120px; padding: 16px 0; }
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.code-section { margin-top: 16px; }
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</style>
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</head>
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<body>
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<div class="container">
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<h1>🟡 049. 二叉树的最近公共祖先 <span class="badge medium">中等</span></h1>
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<p class="subtitle">分类：二叉树 ｜ LeetCode Hot 100</p>
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<!-- 控制面板 -->
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<div class="controls" id="controls">
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<label for="inputArea">输入：</label>
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<input type="text" id="inputArea" placeholder="默认示例，可自定义">
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<button id="applyBtn" class="primary">生成图解</button>
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<select id="exampleSelect"></select>
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<span style="flex:1"></span>
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<button id="prevBtn">◀ 上一步</button>
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<button id="nextBtn">下一步 ▶</button>
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<button id="jumpBtn">⏭ 跳到结果</button>
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<button id="autoBtn">自动播放</button>
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<button id="resetBtn">重置</button>
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</div>
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<!-- 步骤流水线 -->
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<div class="pipeline" id="pipeline"></div>
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<!-- 提示条 -->
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<div class="hint info" id="hintBox">
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<span id="stepInfo"></span><br>
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<span id="hintText"></span>
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</div>
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<!-- 可视化面板 -->
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<div class="panels">
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<div class="panel" id="mainPanel">
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<h3>📊 可视化</h3>
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<div class="vis-area" id="vizArea">点击「生成图解」开始</div>
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</div>
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<div class="panel-grid">
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<div class="panel" id="detailPanel">
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<h3>📝 当前步骤详情</h3>
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<div id="detailContent">等待开始...</div>
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</div>
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<div class="panel" id="resultPanel">
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<h3>✅ 结果</h3>
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<div id="resultContent">等待完成...</div>
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</div>
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</div>
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</div>
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<!-- 代码 -->
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<div class="panel code-section">
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<h3>💻 参考代码（Python）</h3>
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<div id="codeArea"></div>
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</div>
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<footer>Powered by QwenPaw · 图解算法 · LeetCode Hot 100</footer>
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</div>
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<script src="../shared/algo-viz.js"></script>
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<script>
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"use strict";
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(function() {
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// ========== Algorithm Logic ==========
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function arrayToTree(arr) {
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if (!arr || arr.length === 0) return null;
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let idCtr = 0;
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const nodes = arr.map(v => v === null ? null : {val: v, left: null, right: null, _id: 'n' + (idCtr++)});
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for (let i = 0; i < nodes.length; i++) {
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if (!nodes[i]) continue;
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const li = 2*i+1, ri = 2*i+2;
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if (li < nodes.length) nodes[i].left = nodes[li];
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if (ri < nodes.length) nodes[i].right = nodes[ri];
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}
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return nodes[0];
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}
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function treeToArray(root) {
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if (!root) return [];
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const res = [], q = [root];
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while (q.length) {
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const n = q.shift();
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if (n === null) { res.push(null); continue; }
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res.push(n.val); q.push(n.left, n.right);
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}
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while (res.length && res[res.length-1] === null) res.pop();
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return res;
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}
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function deepClone(node) {
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if (!node) return null;
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return {val: node.val, _id: node._id, left: deepClone(node.left), right: deepClone(node.right)};
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}
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const examples = [
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{tree: [3,5,1,6,2,0,8,null,null,7,4], p: 5, q: 1, label: '示例1: p=5, q=1 → LCA=3'},
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{tree: [3,5,1,6,2,0,8,null,null,7,4], p: 5, q: 4, label: '示例2: p=5, q=4 → LCA=5'},
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];
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let root, steps, stepCtrl, pVal, qVal, lcaVal;
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function findNodeByVal(node, val) {
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if (!node) return null;
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if (node.val === val) return node;
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return findNodeByVal(node.left, val) || findNodeByVal(node.right, val);
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}
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function buildSteps(arr, p, q) {
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root = arrayToTree(arr); pVal = p; qVal = q;
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steps = []; lcaVal = null;
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const pNode = findNodeByVal(root, p);
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const qNode = findNodeByVal(root, q);
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const targetHl = {};
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if (pNode) targetHl[pNode._id] = 'active';
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if (qNode) targetHl[qNode._id] = 'active';
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steps.push({stage:'init', hl:Object.assign({}, targetHl), msg:`寻找 ${p} 和 ${q} 的最近公共祖先`});
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function dfs(node) {
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if (!node) return null;
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steps.push({stage:'enter', hl:Object.assign({[node._id]:'current'}, targetHl), msg:`进入节点 ${node.val}`});
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if (node.val === p || node.val === q) {
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steps.push({stage:'found', hl:{[node._id]:'current'}, msg:`节点 ${node.val} 是目标节点 ${node.val===pVal?'p':'q'}！`});
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return node;
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}
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const left = dfs(node.left);
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const right = dfs(node.right);
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if (left && right) {
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lcaVal = node.val;
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steps.push({stage:'lca', hl:{[node._id]:'current'}, msg:`左右子树各找到一个目标，LCA = ${node.val}`, lca:node.val});
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return node;
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}
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const ret = left || right;
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if (ret) {
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steps.push({stage:'return_one', hl:{[node._id]:'visited'}, msg:`节点 ${node.val}：一侧找到目标，向上返回`});
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} else {
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steps.push({stage:'return_none', hl:{[node._id]:'visited'}, msg:`节点 ${node.val}：两侧都没找到，返回 null`});
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}
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return ret;
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}
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dfs(root);
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steps.push({stage:'done', hl:{}, msg:`最近公共祖先 = ${lcaVal !== null ? lcaVal : 'null'}`, lca:lcaVal});
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}
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function render(step) {
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const s = steps[step];
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let viz = renderBinaryTree(root, {highlights: s.hl});
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viz += `<div style="margin-top:8px;font-size:14px;">p = <b style="color:var(--blue);">${pVal}</b> q = <b style="color:var(--purple);">${qVal}</b></div>`;
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$('vizArea').innerHTML = viz;
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$('detailContent').innerHTML = '<div class="calc-block">' + s.msg + '</div>';
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if (s.stage === 'done') {
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$('resultContent').innerHTML = `<div class="final-answer">LCA(${pVal}, ${qVal}) = <b>${s.lca}</b></div>`;
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}
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$('hintText').textContent = s.msg;
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const stages = ['init→初始化','enter→进入','found→找到目标','lca→确定LCA','return_one→返回一侧','return_none→返回空','done→完成'];
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$('pipeline').innerHTML = stages.map(st => {
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const [k,l] = st.split('→');
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return `<span class="pipe-step ${s.stage===k?'active':''}">${l}</span>`;
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}).join('<i>→</i>');
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}
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function init() {
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const sel = $('exampleSelect');
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examples.forEach((e,i) => { sel.innerHTML += `<option value="${i}">${e.label}</option>`; });
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$('inputArea').value = '[3,5,1,6,2,0,8,null,null,7,4], p=5, q=1';
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buildSteps(examples[0].tree, examples[0].p, examples[0].q);
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stepCtrl = new StepController({onStep: render});
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stepCtrl.setSteps(steps.map((_,i)=>i));
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$('stepInfo').textContent = '步骤 1 / ' + steps.length;
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stepCtrl.onStep = (idx) => { render(idx); $('stepInfo').textContent = `步骤 ${idx+1} / ${steps.length}`; };
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$('applyBtn').onclick = () => {
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const m = $('inputArea').value.match(/\[([^\]]+)\].*p\s*=\s*(-?\d+).*q\s*=\s*(-?\d+)/);
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if (!m) { alert('格式: [3,5,1,...], p=5, q=1'); return; }
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const arr = JSON.parse('['+m[1]+']');
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buildSteps(arr, parseInt(m[2]), parseInt(m[3]));
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stepCtrl.setSteps(steps.map((_,i)=>i)); render(0); $('stepInfo').textContent = '步骤 1 / ' + steps.length;
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};
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$('exampleSelect').onchange = () => {
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const e = examples[parseInt($('exampleSelect').value)];
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$('inputArea').value = JSON.stringify(e.tree) + `, p=${e.p}, q=${e.q}`;
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buildSteps(e.tree, e.p, e.q); stepCtrl.setSteps(steps.map((_,i)=>i)); render(0);
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};
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$('prevBtn').onclick = () => stepCtrl.prev();
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$('nextBtn').onclick = () => stepCtrl.next();
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$('jumpBtn').onclick = () => stepCtrl.jumpToEnd();
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$('autoBtn').onclick = () => { const on = stepCtrl.toggleAuto(); $('autoBtn').textContent = on ? '暂停' : '自动播放'; };
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$('resetBtn').onclick = () => { stepCtrl.reset(); $('autoBtn').textContent = '自动播放'; };
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}
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init();
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$('codeArea').innerHTML = renderCode(`def lowestCommonAncestor(root, p, q):
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if not root or root == p or root == q:
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return root
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left = lowestCommonAncestor(root.left, p, q)
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right = lowestCommonAncestor(root.right, p, q)
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if left and right:
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return root
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return left if left else right`, {lang:'Python'});
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})();
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</script>
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</body>
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</html>
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