algorithm-neet-code-top-150-python-visual/visual/1448_count_good_nodes_in_binary_tree.html at main · kimtth/algorithm-neet-code-top-150-python-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
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>LC 1448: Count Good Nodes in Binary Tree - Algorithm Visualization</title>
    <link rel="stylesheet" href="styles.css">
    <script src="https://d3js.org/d3.v7.min.js"></script>
</head>
<body>
    <div class="container">
        <div class="problem-info">
            <h1><span class="problem-number">#1448</span> Count Good Nodes in Binary Tree</h1>
            <p>A node X is "good" if there are no nodes with value greater than X on the path from root to X. Count all good nodes.</p>
            <div class="problem-meta">
                <span class="meta-tag">🌳 Tree</span>
                <span class="meta-tag">🔄 DFS</span>
                <span class="meta-tag">⏱️ O(n)</span>
                <span class="meta-tag">💾 O(h)</span>
            </div>
            <div class="file-ref">
                📄 Python: <code>python/1448_count_good_nodes_in_binary_tree/1448_count_good_nodes_in_binary_tree.py</code>
            </div>
            </div>

        <div class="explanation-panel">
            <h4>🧠 How It Works (Layman's Terms)</h4>
            <p>Track <strong>maximum value seen</strong> on path from root:</p>
            <ul>
                <li><strong>Good Node:</strong> Current value ≥ max value on path</li>
                <li><strong>DFS:</strong> Pass max value to children</li>
                <li><strong>Update:</strong> New max = max(current max, current value)</li>
                <li><strong>Root:</strong> Always good (no ancestors)</li>
            </ul>
        </div>


        <div class="visualization-section">
            <h3>🎬 Step-by-Step Visualization</h3>

            <div class="controls">
                <button class="btn btn-primary" id="startBtn" onclick="start()">▶ Start DFS</button>
                <button class="btn" onclick="stepForward()">Step →</button>
                <button class="btn btn-warning" onclick="reset()">Reset</button>
            </div>

            <div class="status-message" id="statusMessage">
                Click Start to find all good nodes
            </div>

            <div style="display: flex; gap: 30px; flex-wrap: wrap; margin-top: 20px;">
                <div style="flex: 2; min-width: 350px;">
                    <svg id="treeViz" width="100%" height="320"></svg>
                </div>
                <div style="flex: 1; min-width: 200px;">
                    <h4>📊 Current Path</h4>
                    <div id="pathDisplay" style="padding: 15px; background: #fff3e0; border-radius: 12px; margin-bottom: 15px; min-height: 40px;"></div>

                    <h4>📈 Max on Path</h4>
                    <div id="maxDisplay" style="padding: 20px; background: #e3f2fd; border-radius: 12px; margin-bottom: 15px; font-size: 2em; text-align: center; font-weight: bold; color: #2196f3;">
                        -
                    </div>

                    <h4>✅ Good Nodes Count</h4>
                    <div id="countDisplay" style="padding: 20px; background: #e8f5e9; border-radius: 12px; font-size: 2em; text-align: center; font-weight: bold; color: #4caf50;">
                        0
                    </div>

                    <h4 style="margin-top: 15px;">🌟 Good Nodes</h4>
                    <div id="goodNodesDisplay" style="padding: 15px; background: #f3e5f5; border-radius: 12px; min-height: 40px;"></div>
                </div>
            </div>
        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">goodNodes</span>(root):
    <span class="keyword">def</span> <span class="function">dfs</span>(node, max_val):
        <span class="keyword">if not</span> node:
            <span class="keyword">return</span> <span class="number">0</span>

        <span class="comment"># Node is good if val >= max on path</span>
        good = <span class="number">1</span> <span class="keyword">if</span> node.val >= max_val <span class="keyword">else</span> <span class="number">0</span>

        <span class="comment"># Update max for children</span>
        new_max = <span class="function">max</span>(max_val, node.val)

        <span class="keyword">return</span> good + <span class="function">dfs</span>(node.left, new_max) + <span class="function">dfs</span>(node.right, new_max)

    <span class="keyword">return</span> <span class="function">dfs</span>(root, root.val)</pre>
            </div>
        </div>
    </div>

    <script>
        const tree = {
            val: 3, id: 1, x: 250, y: 40,
            left: {
                val: 1, id: 2, x: 130, y: 110,
                left: { val: 3, id: 4, x: 70, y: 180, left: null, right: null },
                right: null
            },
            right: {
                val: 4, id: 3, x: 370, y: 110,
                left: { val: 1, id: 5, x: 310, y: 180, left: null, right: null },
                right: { val: 5, id: 6, x: 430, y: 180, left: null, right: null }
            }
        };

        let visited = new Set();
        let goodNodes = new Set();
        let currentNode = null;
        let currentPath = [];
        let maxOnPath = -Infinity;
        let goodCount = 0;
        let isRunning = false;
        let stepIndex = 0;
        let steps = [];

        function flattenTree(node, arr = []) {
            if (!node) return arr;
            arr.push(node);
            flattenTree(node.left, arr);
            flattenTree(node.right, arr);
            return arr;
        }

        function precomputeSteps() {
            steps = [];

            function dfs(node, path, maxVal) {
                if (!node) return;

                const newPath = [...path, node.val];
                const isGood = node.val >= maxVal;
                const newMax = Math.max(maxVal, node.val);

                steps.push({
                    type: 'visit',
                    nodeId: node.id,
                    nodeVal: node.val,
                    path: newPath,
                    maxOnPath: maxVal,
                    isGood,
                    message: `Visit ${node.val}: ${node.val} ${isGood ? '≥' : '<'} ${maxVal} → ${isGood ? 'GOOD ✓' : 'Not good'}`
                });

                dfs(node.left, newPath, newMax);
                dfs(node.right, newPath, newMax);

                steps.push({
                    type: 'backtrack',
                    path: path,
                    maxOnPath: maxVal,
                    message: `Backtrack from ${node.val}`
                });
            }

            dfs(tree, [], -Infinity);

            // Count total good nodes
            let total = 0;
            steps.forEach(s => {
                if (s.type === 'visit' && s.isGood) total++;
            });

            steps.push({
                type: 'done',
                message: `Done! Total good nodes: ${total}`
            });
        }

        function render() {
            const svg = d3.select("#treeViz");
            svg.selectAll("*").remove();

            const container = svg.node().parentElement;
            const width = container.clientWidth;
            const height = 320;
            svg.attr("viewBox", `0 0 ${width} ${height}`);

            const nodes = flattenTree(tree);
            const g = svg.append("g").attr("transform", `translate(${(width - 500) / 2}, 0)`);

            // Draw edges
            function drawEdges(node) {
                if (!node) return;
                if (node.left) {
                    g.append("line")
                        .attr("x1", node.x).attr("y1", node.y)
                        .attr("x2", node.left.x).attr("y2", node.left.y)
                        .attr("stroke", "#ccc").attr("stroke-width", 2);
                    drawEdges(node.left);
                }
                if (node.right) {
                    g.append("line")
                        .attr("x1", node.x).attr("y1", node.y)
                        .attr("x2", node.right.x).attr("y2", node.right.y)
                        .attr("stroke", "#ccc").attr("stroke-width", 2);
                    drawEdges(node.right);
                }
            }
            drawEdges(tree);

            // Draw nodes
            nodes.forEach(node => {
                const isVisited = visited.has(node.id);
                const isGood = goodNodes.has(node.id);
                const isCurrent = currentNode === node.id;

                let fill = '#667eea';
                if (isVisited) fill = '#90caf9';
                if (isGood) fill = '#4caf50';
                if (isCurrent) fill = '#ff9800';

                g.append("circle")
                    .attr("cx", node.x).attr("cy", node.y).attr("r", 25)
                    .attr("fill", fill)
                    .attr("stroke", isCurrent ? '#e65100' : '#5a6fd6')
                    .attr("stroke-width", isCurrent ? 4 : 2);

                g.append("text")
                    .attr("x", node.x).attr("y", node.y + 6)
                    .attr("text-anchor", "middle")
                    .attr("fill", "white").attr("font-weight", "bold").attr("font-size", "16px")
                    .text(node.val);

                if (isGood && !isCurrent) {
                    g.append("text")
                        .attr("x", node.x + 25).attr("y", node.y - 15)
                        .attr("font-size", "18px")
                        .text("✓");
                }
            });

            updateDisplays();
        }

        function updateDisplays() {
            const pathContainer = document.getElementById('pathDisplay');
            pathContainer.innerHTML = currentPath.length > 0
                ? currentPath.map((v, i) => `<span style="background: ${i === currentPath.length - 1 ? '#ff9800' : '#ffcc80'}; padding: 5px 12px; margin: 2px; border-radius: 15px; display: inline-block;">${v}</span>`).join(' → ')
                : '<span style="color: #999;">(empty)</span>';

            document.getElementById('maxDisplay').textContent = maxOnPath === -Infinity ? '-∞' : maxOnPath;
            document.getElementById('countDisplay').textContent = goodCount;

            const goodContainer = document.getElementById('goodNodesDisplay');
            goodContainer.innerHTML = goodNodes.size > 0
                ? Array.from(goodNodes).map(id => {
                    const node = flattenTree(tree).find(n => n.id === id);
                    return `<span style="background: #4caf50; color: white; padding: 5px 12px; margin: 2px; border-radius: 15px; display: inline-block;">${node.val}</span>`;
                }).join(' ')
                : '<span style="color: #999;">(none yet)</span>';
        }

        function stepForward() {
            if (stepIndex >= steps.length) return;

            const step = steps[stepIndex];

            if (step.type === 'visit') {
                visited.add(step.nodeId);
                currentNode = step.nodeId;
                currentPath = step.path;
                maxOnPath = step.maxOnPath;
                if (step.isGood) {
                    goodNodes.add(step.nodeId);
                    goodCount++;
                }
            } else if (step.type === 'backtrack') {
                currentPath = step.path;
                maxOnPath = step.maxOnPath;
                currentNode = null;
            } else if (step.type === 'done') {
                currentNode = null;
                isRunning = false;
                document.getElementById('startBtn').textContent = '▶ Start DFS';
            }

            document.getElementById('statusMessage').textContent = step.message;
            stepIndex++;
            render();
        }

        async function start() {
            if (isRunning) {
                isRunning = false;
                document.getElementById('startBtn').textContent = '▶ Start DFS';
                return;
            }

            isRunning = true;
            document.getElementById('startBtn').textContent = '⏸ Pause';

            while (stepIndex < steps.length && isRunning) {
                stepForward();
                await new Promise(r => setTimeout(r, 600));
            }
        }

        function reset() {
            isRunning = false;
            stepIndex = 0;
            visited = new Set();
            goodNodes = new Set();
            currentNode = null;
            currentPath = [];
            maxOnPath = -Infinity;
            goodCount = 0;

            document.getElementById('statusMessage').textContent = 'Click Start to find all good nodes';
            document.getElementById('startBtn').textContent = '▶ Start DFS';

            precomputeSteps();
            render();
        }

        reset();
        window.addEventListener('resize', render);
    </script>
</body>
</html>