211 lines
8.1 KiB
HTML
211 lines
8.1 KiB
HTML
<!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>047. 从前序与中序遍历序列构造二叉树 – 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>🟡 047. 从前序与中序遍历序列构造二叉树 <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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{preorder: [3,9,20,15,7], inorder: [9,3,15,20,7], label: '示例1: pre=[3,9,20,15,7] in=[9,3,15,20,7]'},
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{preorder: [-1], inorder: [-1], label: '示例2: 单节点'},
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];
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let preo, ino, steps, stepCtrl, builtRoot;
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let idCtr;
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function buildSteps(pre, ine) {
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preo = [...pre]; ino = [...ine];
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steps = []; idCtr = 0;
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const inMap = {};
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ine.forEach((v,i) => inMap[v] = i);
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steps.push({stage:'init', hlPre:{}, hlIn:{}, msg:'前序找根，中序分左右，递归构造'});
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function build(pl, pr, il, ir) {
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if (pl > pr) return null;
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const rootVal = pre[pl];
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const node = {val: rootVal, _id: 'n' + (idCtr++), left: null, right: null};
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const inIdx = inMap[rootVal];
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const leftSize = inIdx - il;
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const hlPre = {}, hlIn = {};
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hlPre[pl] = 'orange';
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for (let i = pl+1; i <= pr; i++) hlPre[i] = 'default';
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for (let i = il; i <= ir; i++) hlIn[i] = i === inIdx ? 'orange' : (i < inIdx ? 'blue' : 'purple');
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steps.push({stage:'select', hlPre, hlIn, msg:`根 = pre[${pl}]=${rootVal}，中序位置=${inIdx}，左子树 ${leftSize} 个，右子树 ${pr-pl-leftSize} 个`, rootVal, inIdx});
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node.left = build(pl + 1, pl + leftSize, il, inIdx - 1);
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node.right = build(pl + leftSize + 1, pr, inIdx + 1, ir);
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return node;
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}
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builtRoot = build(0, pre.length - 1, 0, ine.length - 1);
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steps.push({stage:'done', hlPre:{}, hlIn:{}, msg:'构造完成！'});
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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 = '<div><b>前序：</b></div>';
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viz += renderArray(preo, {highlights: s.hlPre || {}});
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viz += '<div style="margin-top:6px;"><b>中序：</b></div>';
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viz += renderArray(ino, {highlights: s.hlIn || {}});
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if (s.inIdx !== undefined) {
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viz += `<div class="partition-legend" style="margin-top:6px;">
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<span><span class="dot-lg" style="background:var(--blue-light);"></span> 左子树</span>
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<span><span class="dot-lg" style="background:var(--orange-light);"></span> 根</span>
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<span><span class="dot-lg" style="background:var(--purple-light);"></span> 右子树</span>
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</div>`;
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}
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if (builtRoot) {
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viz += '<div style="margin-top:10px;"><b>构造中的树：</b></div>';
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viz += renderBinaryTree(builtRoot, {highlights: {}});
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}
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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">构造的树 = <b>[${treeToArray(builtRoot)}]</b></div>`;
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}
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$('hintText').textContent = s.msg;
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const stages = ['init→初始化','select→选根','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 = 'pre=[3,9,20,15,7] in=[9,3,15,20,7]';
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buildSteps(examples[0].preorder, examples[0].inorder);
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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(/pre=\[([^\]]+)\].*in=\[([^\]]+)\]/);
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if (!m) { alert('格式: pre=[3,9,20,15,7] in=[9,3,15,20,7]'); return; }
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const pre = JSON.parse('['+m[1]+']'), ine = JSON.parse('['+m[2]+']');
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buildSteps(pre, ine); 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 = `pre=[${e.preorder}] in=[${e.inorder}]`;
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buildSteps(e.preorder, e.inorder); 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 buildTree(preorder, inorder):
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in_map = {v: i for i, v in enumerate(inorder)}
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def build(pl, pr, il, ir):
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if pl > pr: return None
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root_val = preorder[pl]
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idx = in_map[root_val]
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left_size = idx - il
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root = TreeNode(root_val)
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root.left = build(pl+1, pl+left_size, il, idx-1)
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root.right = build(pl+left_size+1, pr, idx+1, ir)
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return root
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return build(0, len(preorder)-1, 0, len(inorder)-1)`, {lang:'Python'});
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})();
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</script>
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</body>
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</html> |