leetcode-visual/T034-binary-search-range.html at main · houbb/leetcode-visual · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>🔍 T34 可视化：查找元素的第一个和最后一个位置</title>
  <style>
    body {
      font-family: 'Segoe UI', sans-serif;
      background: #f4f6f8;
      margin: 0;
      padding: 20px;
    }
    .container {
      max-width: 800px;
      margin: auto;
    }
    h1 {
      text-align: center;
      color: #333;
    }
    input, button {
      padding: 10px;
      margin: 5px 0;
      font-size: 16px;
    }
    .array-box {
      display: flex;
      justify-content: center;
      flex-wrap: wrap;
      margin: 20px 0;
    }
    .item {
      width: 40px;
      height: 40px;
      border: 2px solid #ccc;
      display: flex;
      align-items: center;
      justify-content: center;
      margin: 4px;
      background-color: white;
      transition: background-color 0.3s;
    }
    .highlight {
      background-color: #ffeb3b;
    }
    .found {
      background-color: #8bc34a !important;
    }
    .not-found {
      background-color: #e57373 !important;
    }
    .card {
      background: white;
      border-radius: 8px;
      padding: 20px;
      box-shadow: 0 2px 10px rgba(0,0,0,0.1);
      margin-top: 20px;
    }
    .footer {
      margin-top: 30px;
      text-align: center;
    }
    .back {
      margin-top: 20px;
      display: inline-block;
      padding: 8px 12px;
      background: #2196f3;
      color: white;
      text-decoration: none;
      border-radius: 5px;
    }
    .log {
      background: #1e1e1e;
      color: #dcdcdc;
      font-family: monospace;
      padding: 10px;
      height: 200px;
      overflow-y: auto;
      margin-top: 10px;
      border-radius: 5px;
    }
    .log p {
      margin: 4px 0;
    }
  </style>
</head>
<body>
  <div class="container">
    <h1>🔍 T34 可视化：查找元素的第一个和最后一个位置</h1>

    <label>数组（用逗号分隔）：</label><br>
    <input type="text" id="arrayInput" value="5,7,7,8,8,10" size="50"/><br>
    <label>目标值：</label><br>
    <input type="number" id="targetInput" value="8"/><br>
    <button onclick="visualize()">开始可视化</button>

    <div class="array-box" id="arrayBox"></div>

    <div class="log" id="logBox"></div>

    <div class="card" id="resultCard" style="display:none;">
      <h3>查找结果</h3>
      <p id="resultText"></p>
    </div>

    <div class="footer">
      <a href="index.html" class="back">⬅ 返回首页</a>
    </div>
  </div>

  <script>
    function sleep(ms) {
      return new Promise(resolve => setTimeout(resolve, ms));
    }

    function log(msg) {
      const logBox = document.getElementById("logBox");
      const p = document.createElement("p");
      p.textContent = msg;
      logBox.appendChild(p);
      logBox.scrollTop = logBox.scrollHeight;
    }

    async function visualize() {
      const input = document.getElementById("arrayInput").value;
      const target = parseInt(document.getElementById("targetInput").value);
      const array = input.split(",").map(n => parseInt(n.trim()));
      const box = document.getElementById("arrayBox");
      const resultCard = document.getElementById("resultCard");
      const resultText = document.getElementById("resultText");
      const logBox = document.getElementById("logBox");

      resultCard.style.display = "none";
      box.innerHTML = "";
      logBox.innerHTML = "";

      array.forEach(num => {
        const div = document.createElement("div");
        div.className = "item";
        div.innerText = num;
        box.appendChild(div);
      });

      const items = document.querySelectorAll(".item");

      async function binarySearchBoundary(leftToRight) {
        let left = 0;
        let right = array.length - 1;
        let result = -1;
        log(`🔍 开始 ${leftToRight ? "查找左边界" : "查找右边界"}...`);

        while (left <= right) {
          let mid = Math.floor((left + right) / 2);
          log(`➡️ left=${left}, right=${right}, mid=${mid}, nums[mid]=${array[mid]}`);

          items[mid].classList.add("highlight");
          await sleep(700);
          items[mid].classList.remove("highlight");

          if (array[mid] === target) {
            result = mid;
            log(`✅ nums[mid] == target，记录位置为 ${mid}`);
            if (leftToRight) {
              right = mid - 1;
              log(`🔁 向左查找更小位置：right = ${right}`);
            } else {
              left = mid + 1;
              log(`🔁 向右查找更大位置：left = ${left}`);
            }
          } else if (array[mid] < target) {
            left = mid + 1;
            log(`⬆️ nums[mid] < target，向右查找：left = ${left}`);
          } else {
            right = mid - 1;
            log(`⬇️ nums[mid] > target，向左查找：right = ${right}`);
          }
        }

        log(`🎯 ${leftToRight ? "左边界" : "右边界"} 查找结束，结果：${result}`);
        return result;
      }

      const first = await binarySearchBoundary(true);
      const last = await binarySearchBoundary(false);

      if (first !== -1) {
        items[first].classList.add("found");
        if (last !== first) items[last].classList.add("found");
      } else {
        array.forEach((_, i) => items[i].classList.add("not-found"));
      }

      resultCard.style.display = "block";
      resultText.innerText = `结果区间：[${first}, ${last}]`;
    }
  </script>
</body>
</html>