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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>013. 最大子数组和 – 图解</title>
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<link rel="stylesheet" href="../shared/style.css">
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<style>
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.vis-area { min-height: 160px; padding: 16px 0; }
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.code-section { margin-top: 16px; }
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.tag { display: inline-block; padding: 2px 8px; border-radius: 6px; font-size: 12px; font-weight: 600; margin: 0 3px; }
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.tag.cur { background: #fff7ed; color: #9a3412; border: 1px solid #f59e0b; }
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.tag.best { background: #dcfce7; color: #166534; border: 1px solid #16a34a; }
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.summary-row { display: flex; gap: 24px; flex-wrap: wrap; margin-top: 12px; }
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.summary-item { display: flex; align-items: center; gap: 6px; font-size: 14px; }
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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>🟡 013. 最大子数组和 <span class="badge medium">中等</span></h1>
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<p class="subtitle">分类：普通数组 ｜ LeetCode Hot 100 ｜ Kadane 算法</p>
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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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<div class="pipeline" id="pipeline"></div>
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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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<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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<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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const examples = [
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{input: [-2,1,-3,4,-1,2,1,-5,4], label: '示例1: [-2,1,-3,4,-1,2,1,-5,4]'},
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{input: [1], label: '示例2: [1]'},
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{input: [5,4,-1,7,8], label: '示例3: [5,4,-1,7,8]'},
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{input: [-1,-2,-3,-4], label: '全负: [-1,-2,-3,-4]'},
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];
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let nums, steps, stepCtrl;
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function buildSteps(arr) {
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nums = [...arr];
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steps = [];
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const n = nums.length;
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let curSum = nums[0], maxSum = nums[0];
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let curStart = 0, curEnd = 0;
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let bestStart = 0, bestEnd = 0;
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steps.push({
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stage:'init', i:0, curSum, maxSum,
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curStart:0, curEnd:0, bestStart:0, bestEnd:0,
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msg:`初始化：current = max = nums[0] = ${nums[0]}，当前子数组范围 [0,0]`
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});
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for (let i = 1; i < n; i++) {
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const extendSum = curSum + nums[i];
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if (extendSum > nums[i]) {
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curSum = extendSum;
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curEnd = i;
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steps.push({
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stage:'extend', i, curSum, maxSum,
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curStart, curEnd, bestStart, bestEnd,
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msg:`i=${i}: nums[${i}]=${nums[i]}，延伸更优 (${curSum - nums[i]})+${nums[i]}=${curSum} ≥ ${nums[i]}，当前子数组 [${curStart},${curEnd}]，curSum=${curSum}`
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});
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} else {
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curSum = nums[i];
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curStart = i; curEnd = i;
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steps.push({
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stage:'restart', i, curSum, maxSum,
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curStart, curEnd, bestStart, bestEnd,
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msg:`i=${i}: nums[${i}]=${nums[i]}，重新开始更优 (${extendSum - nums[i]})+${nums[i]}=${extendSum} < ${nums[i]}，新子数组 [${curStart},${curEnd}]，curSum=${curSum}`
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});
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}
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if (curSum > maxSum) {
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const oldMax = maxSum;
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maxSum = curSum;
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bestStart = curStart; bestEnd = curEnd;
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steps.push({
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stage:'update_max', i, curSum, maxSum,
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curStart, curEnd, bestStart, bestEnd,
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msg:`i=${i}: curSum=${curSum} > maxSum=${oldMax}，更新最大子数组和为 ${maxSum}，范围 [${bestStart},${bestEnd}]`
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});
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}
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}
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steps.push({
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stage:'done', i:n-1, curSum, maxSum,
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curStart, curEnd, bestStart, bestEnd,
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msg:`遍历完毕，最大子数组和 = ${maxSum}，范围 [${bestStart},${bestEnd}]`
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});
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}
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function render(step) {
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const s = steps[step];
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// Build highlights: current subarray = orange, best subarray = green override
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const hl = {};
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for (let i = s.curStart; i <= s.curEnd; i++) hl[i] = 'orange';
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for (let i = s.bestStart; i <= s.bestEnd; i++) hl[i] = 'green';
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if (s.i >= 0 && s.i < nums.length) hl[s.i] = 'active';
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const pointers = {};
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if (s.i >= 0) pointers['i'] = s.i;
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let viz = '<div style="margin-bottom:8px;font-size:13px;color:#475569;">原始数组</div>';
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viz += renderArray(nums, {highlights: hl, pointers});
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// Subarray labels below
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viz += '<div style="margin-top:12px;display:flex;gap:16px;flex-wrap:wrap;font-size:13px;">';
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viz += `<span class="tag cur">当前子数组 [${s.curStart},${s.curEnd}] 和 = ${s.curSum}</span>`;
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viz += `<span class="tag best">最大子数组 [${s.bestStart},${s.bestEnd}] 和 = ${s.maxSum}</span>`;
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viz += '</div>';
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// DP formula
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viz += '<div class="formula-box" style="margin-top:12px;">';
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viz += `<code>dp[i] = max(nums[i], dp[i-1] + nums[i])</code><br>`;
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if (s.stage !== 'init') {
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viz += `当前 i=${s.i}: dp[${s.i}] = max(${nums[s.i]}, ${s.curSum === nums[s.i] && s.stage==='restart' ? 'prev+'+nums[s.i] : 'prev+' + nums[s.i]}) = <b>${s.curSum}</b>`;
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}
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viz += '</div>';
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$('vizArea').innerHTML = viz;
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// Detail panel
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let detail = '<div class="calc-block">' + s.msg + '</div>';
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detail += '<div class="summary-row">';
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detail += `<div class="summary-item"><span class="tag cur">curSum</span> <b>${s.curSum}</b></div>`;
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detail += `<div class="summary-item"><span class="tag best">maxSum</span> <b>${s.maxSum}</b></div>`;
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detail += '</div>';
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$('detailContent').innerHTML = detail;
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// Result
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if (s.stage === 'done') {
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const sub = nums.slice(s.bestStart, s.bestEnd + 1);
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$('resultContent').innerHTML = `<div class="final-answer">
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最大子数组和 = <b>${s.maxSum}</b><br>
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子数组: [${sub.join(', ')}]<br>
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范围: 索引 [${s.bestStart}, ${s.bestEnd}]
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<div class="complexity">时间复杂度 O(n) ｜ 空间复杂度 O(1) ｜ Kadane 算法</div>
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</div>`;
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}
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$('hintText').textContent = s.msg;
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const stages = [
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['init','初始化'],['extend','延伸'],['restart','重新开始'],['update_max','更新最大'],['done','完成']
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];
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$('pipeline').innerHTML = stages.map(([k,l]) =>
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`<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 = JSON.stringify(examples[0].input);
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buildSteps(examples[0].input);
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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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try {
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const arr = JSON.parse($('inputArea').value);
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if (!Array.isArray(arr) || arr.length === 0) throw new Error();
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buildSteps(arr); stepCtrl.setSteps(steps.map((_,i)=>i)); render(0);
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$('stepInfo').textContent = '步骤 1 / ' + steps.length;
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} catch(e) { alert('请输入合法非空 JSON 数组，例如 [-2,1,-3,4,-1,2,1,-5,4]'); }
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};
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$('exampleSelect').onchange = () => {
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const e = examples[parseInt($('exampleSelect').value)];
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$('inputArea').value = JSON.stringify(e.input);
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buildSteps(e.input); stepCtrl.setSteps(steps.map((_,i)=>i)); render(0);
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};
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$('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 maxSubArray(nums):
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cur = max_sum = nums[0]
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for i in range(1, len(nums)):
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# dp[i] = max(nums[i], dp[i-1] + nums[i])
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cur = max(nums[i], cur + nums[i])
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max_sum = max(max_sum, cur)
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return max_sum`, {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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