249 lines
11 KiB
HTML
249 lines
11 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>065. 在排序数组中查找元素的第一个和最后一个位置 – 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: 120px; padding: 16px 0; }
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.code-section { margin-top: 16px; }
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.phase-tag { display:inline-block; padding:2px 10px; border-radius:999px; font-size:12px; font-weight:600; margin-bottom:8px; }
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.phase-tag.left { background:#dbeafe; color:#1e40af; }
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.phase-tag.right { background:#dcfce7; color:#166534; }
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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>🟡 065. 在排序数组中查找元素的第一个和最后一个位置 <span class="badge medium">中等</span></h1>
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<p class="subtitle">分类：二分查找 ｜ LeetCode Hot 100</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="nums=[5,7,7,8,8,10], target=8">
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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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{nums:[5,7,7,8,8,10], target:8, label:'示例1: target=8'},
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{nums:[5,7,7,8,8,10], target:6, label:'示例2: target=6'},
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{nums:[], target:0, label:'示例3: 空数组'},
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];
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let numsArr, target, steps, stepCtrl;
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function buildSteps(nums, tgt) {
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numsArr = nums; target = tgt;
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steps = [];
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if (nums.length === 0) {
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steps.push({phase:'done', stage:'empty', msg:'数组为空，返回 [-1, -1]', leftIdx:-1, rightIdx:-1});
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return;
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}
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// Phase 1: find left boundary
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steps.push({phase:'left', stage:'leftInit', msg:`第一步：查找左边界（第一个等于 ${tgt} 的位置）`, left:0, right:nums.length-1, mid:-1, leftIdx:-1, rightIdx:-1});
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let lL = 0, lR = nums.length - 1, leftIdx = -1;
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while (lL <= lR) {
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const mid = Math.floor((lL + lR) / 2);
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steps.push({phase:'left', stage:'leftCalc', msg:`左边界搜索：mid=${mid}，nums[${mid}]=${nums[mid]}`, left:lL, right:lR, mid, leftIdx:-1, rightIdx:-1});
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if (nums[mid] >= tgt) {
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const action = nums[mid] === tgt ? `= ${tgt}，可能不是最左，继续向左` : `> ${tgt}，目标在左侧`;
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steps.push({phase:'left', stage:'leftMove', msg:`nums[${mid}]=${nums[mid]} ${action}，right = ${mid}-1 = ${mid-1}`, left:lL, right:mid-1, mid, leftIdx:-1, rightIdx:-1});
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if (nums[mid] === tgt) leftIdx = mid;
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lR = mid - 1;
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} else {
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steps.push({phase:'left', stage:'leftMove', msg:`nums[${mid}]=${nums[mid]} < ${tgt}，目标在右侧，left = ${mid}+1 = ${mid+1}`, left:mid+1, right:lR, mid, leftIdx:-1, rightIdx:-1});
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lL = mid + 1;
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}
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}
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steps.push({phase:'left', stage:'leftDone', msg:`左边界搜索完成，leftIdx = ${leftIdx}`, left:lL, right:lR, mid:-1, leftIdx, rightIdx:-1});
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if (leftIdx === -1) {
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steps.push({phase:'done', stage:'notFound', msg:`未找到 ${tgt}，返回 [-1, -1]`, leftIdx:-1, rightIdx:-1});
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return;
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}
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// Phase 2: find right boundary
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let rL = 0, rR = nums.length - 1, rightIdx = -1;
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steps.push({phase:'right', stage:'rightInit', msg:`第二步：查找右边界（最后一个等于 ${tgt} 的位置）`, left:0, right:nums.length-1, mid:-1, leftIdx, rightIdx:-1});
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while (rL <= rR) {
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const mid = Math.floor((rL + rR) / 2);
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steps.push({phase:'right', stage:'rightCalc', msg:`右边界搜索：mid=${mid}，nums[${mid}]=${nums[mid]}`, left:rL, right:rR, mid, leftIdx, rightIdx:-1});
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if (nums[mid] <= tgt) {
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const action = nums[mid] === tgt ? `= ${tgt}，可能不是最右，继续向右` : `< ${tgt}，目标在右侧`;
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steps.push({phase:'right', stage:'rightMove', msg:`nums[${mid}]=${nums[mid]} ${action}，left = ${mid}+1 = ${mid+1}`, left:mid+1, right:rR, mid, leftIdx, rightIdx:-1});
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if (nums[mid] === tgt) rightIdx = mid;
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rL = mid + 1;
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} else {
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steps.push({phase:'right', stage:'rightMove', msg:`nums[${mid}]=${nums[mid]} > ${tgt}，目标在左侧，right = ${mid}-1 = ${mid-1}`, left:rL, right:mid-1, mid, leftIdx, rightIdx:-1});
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rR = mid - 1;
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}
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}
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steps.push({phase:'right', stage:'rightDone', msg:`右边界搜索完成，rightIdx = ${rightIdx}`, left:rL, right:rR, mid:-1, leftIdx, rightIdx});
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steps.push({phase:'done', stage:'done', msg:`结果：[${leftIdx}, ${rightIdx}]`, leftIdx, rightIdx});
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}
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function render(step) {
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const s = steps[step];
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const arr = numsArr;
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if (!arr.length) {
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$('vizArea').innerHTML = '<div class="formula-box">数组为空</div>';
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$('detailContent').innerHTML = `<div class="calc-block">${s.msg}</div>`;
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$('resultContent').innerHTML = '<div class="final-answer" style="border-color:#f87171;background:#fef2f2;">返回 [-1, -1]</div>';
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$('hintText').textContent = s.msg;
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return;
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}
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const hl = highlightRange(arr, s.left, s.right, 'cyan');
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if (s.mid >= 0 && s.mid < arr.length) hl[s.mid] = 'orange';
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// highlight found boundaries
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if (s.leftIdx >= 0) hl[s.leftIdx] = 'green';
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if (s.rightIdx >= 0 && s.rightIdx !== s.leftIdx) hl[s.rightIdx] = 'green';
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const pointers = {};
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if (s.left >= 0 && s.left < arr.length) pointers['L'] = s.left;
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if (s.right >= 0 && s.right < arr.length) pointers['R'] = s.right;
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if (s.mid >= 0 && s.mid < arr.length) pointers['mid'] = s.mid;
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let viz = `<div class="phase-tag ${s.phase==='left'?'left':'right'}">${s.phase==='left'?'阶段一：找左边界':s.phase==='right'?'阶段二：找右边界':'完成'}</div>`;
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viz += renderArray(arr, {highlights: hl, pointers});
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if (s.mid >= 0 && s.mid < arr.length) {
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viz += `<div style="margin-top:6px;font-size:13px;">nums[${s.mid}] = ${arr[s.mid]} vs target = ${target} → ${arr[s.mid]===target?'相等':arr[s.mid]<target?'小于':'大于'}</div>`;
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}
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if (s.leftIdx >= 0 || s.rightIdx >= 0) {
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viz += `<div class="current-answer">左边界 = ${s.leftIdx} 右边界 = ${s.rightIdx}</div>`;
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}
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$('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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$('resultContent').innerHTML = `<div class="final-answer">返回 <b>[${s.leftIdx}, ${s.rightIdx}]</b><br>时间复杂度 O(log n)</div>`;
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} else if (s.stage === 'notFound') {
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$('resultContent').innerHTML = `<div class="final-answer" style="border-color:#f87171;background:#fef2f2;">返回 <b>[-1, -1]</b></div>`;
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}
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$('hintText').textContent = s.msg;
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const stages = ['leftInit→左搜索','leftCalc→左计算','leftMove→左移动','leftDone→左完成','rightInit→右搜索','rightCalc→右计算','rightMove→右移动','rightDone→右完成','done→完成','notFound→未找到'];
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$('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 = 'nums=[5,7,7,8,8,10], target=8';
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buildSteps(examples[0].nums, examples[0].target);
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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 m = $('inputArea').value.match(/nums=\[([^\]]+)\].*target=(-?\d+)/);
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if (!m) { alert('格式: nums=[5,7,7,8,8,10], target=8'); return; }
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const arr = m[1].split(',').map(Number);
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const tgt = parseInt(m[2]);
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buildSteps(arr, tgt);
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stepCtrl.setSteps(steps.map((_,i)=>i)); render(0);
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$('stepInfo').textContent = `步骤 1 / ${steps.length}`;
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} catch(e) { alert('输入格式错误'); }
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};
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$('exampleSelect').onchange = () => {
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const e = examples[parseInt($('exampleSelect').value)];
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$('inputArea').value = `nums=[${e.nums}], target=${e.target}`;
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buildSteps(e.nums, e.target);
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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 searchRange(nums, target):
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def findLeft():
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l, r = 0, len(nums) - 1
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idx = -1
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while l <= r:
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mid = (l + r) // 2
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if nums[mid] >= target:
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if nums[mid] == target:
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idx = mid
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r = mid - 1
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else:
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l = mid + 1
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return idx
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def findRight():
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l, r = 0, len(nums) - 1
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idx = -1
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while l <= r:
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mid = (l + r) // 2
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if nums[mid] <= target:
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if nums[mid] == target:
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idx = mid
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l = mid + 1
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else:
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r = mid - 1
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return idx
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return [findLeft(), findRight()]`, {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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