algorithm-neet-code-top-150-python-visual/visual/1249_min_remove_parentheses.html at main · kimtth/algorithm-neet-code-top-150-python-visual · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Minimum Remove to Make Valid Parentheses - LeetCode 1249</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">#1249</span> Minimum Remove to Make Valid Parentheses</h1>
            <p>Remove the minimum number of parentheses to make the string valid. Use a stack to track unmatched parentheses!</p>
            <div class="problem-meta">
                <span class="meta-tag">📚 Stack</span>
                <span class="meta-tag">🔤 String</span>
                <span class="meta-tag">⏱️ O(n)</span>
            </div>
            <div class="file-ref">
                📄 Python: <a href="../python/1249_minimum_remove_to_make_valid_parentheses/1249_minimum_remove_to_make_valid_parentheses.py">1249_minimum_remove_to_make_valid_parentheses.py</a>
            </div>
            </div>

        <div class="explanation-panel">
            <h4>💡 How It Works (Layman's Terms)</h4>
            <ul>
                <li><strong>Valid parentheses:</strong> Every '(' has a matching ')' that comes after it</li>
                <li><strong>Phase 1 - Scan:</strong> Go through string, use stack to track unmatched '('</li>
                <li><strong>When we see '(':</strong> Push its index to stack (might need to be removed)</li>
                <li><strong>When we see ')':</strong> If stack has a '(', pop it (they match!). Otherwise, mark ')' for removal.</li>
                <li><strong>After scan:</strong> Any remaining indices in stack are unmatched '(' - mark for removal</li>
                <li><strong>Phase 2 - Build:</strong> Skip characters at removal indices, keep everything else</li>
            </ul>
        </div>


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

            <div class="controls">
                <button class="btn btn-primary" id="stepBtn" onclick="step()">Step</button>
                <button class="btn btn-success" id="autoBtn" onclick="toggleAuto()">Auto Run</button>
                <button class="btn btn-warning" onclick="reset()">Reset</button>
            </div>

            <div class="phase-indicator">
                <div class="phase-box" id="scanPhase">
                    <div class="phase-title">Phase 1: Scan</div>
                    <div class="phase-description">Find unmatched parentheses</div>
                </div>
                <div class="phase-box" id="buildPhase">
                    <div class="phase-title">Phase 2: Build</div>
                    <div class="phase-description">Construct result string</div>
                </div>
            </div>

            <div class="status-message" id="statusMessage">
                Click "Step" or "Auto Run" to remove invalid parentheses
            </div>

            <div class="array-section">
                <div class="array-label">Input String:</div>
                <div class="array-container" id="stringContainer"></div>
            </div>

            <div class="array-section">
                <div class="array-label">Stack (indices of unmatched '('):</div>
                <div class="stack-container" id="stackContainer" style="flex-direction: row; min-height: 60px;"></div>
            </div>

            <div class="array-section">
                <div class="array-label">Remove Indices:</div>
                <div id="removeContainer" style="font-family: monospace; font-size: 1.1em; padding: 10px; background: #ffebee; border-radius: 8px; min-height: 30px;"></div>
            </div>

            <div class="array-section">
                <div class="array-label">Result:</div>
                <div id="resultContainer" style="font-family: monospace; font-size: 1.4em; padding: 15px; background: #e8f5e9; border-radius: 8px; min-height: 40px;"></div>
            </div>
        </div>

        <div class="code-section">
            <h3>💻 Python Solution</h3>
            <div class="code-block">
                <pre><span class="keyword">def</span> <span class="function">minRemoveToMakeValid</span>(self, s: <span class="class-name">str</span>) -> <span class="class-name">str</span>:
    remove_indices = <span class="function">set</span>()
    stack = []  <span class="comment"># stores indices of unmatched '('</span>

    <span class="keyword">for</span> i <span class="keyword">in</span> <span class="function">range</span>(<span class="function">len</span>(s)):
        <span class="keyword">if</span> s[i] == <span class="string">'('</span>:
            stack.<span class="function">append</span>(i)
        <span class="keyword">elif</span> s[i] == <span class="string">')'</span>:
            <span class="keyword">if</span> <span class="keyword">not</span> stack:
                remove_indices.<span class="function">add</span>(i)  <span class="comment"># unmatched ')'</span>
            <span class="keyword">else</span>:
                stack.<span class="function">pop</span>()  <span class="comment"># matched pair</span>

    <span class="comment"># Remaining in stack are unmatched '('</span>
    <span class="keyword">while</span> stack:
        remove_indices.<span class="function">add</span>(stack.<span class="function">pop</span>())

    result = []
    <span class="keyword">for</span> i <span class="keyword">in</span> <span class="function">range</span>(<span class="function">len</span>(s)):
        <span class="keyword">if</span> i <span class="keyword">not in</span> remove_indices:
            result.<span class="function">append</span>(s[i])

    <span class="keyword">return</span> <span class="string">''</span>.<span class="function">join</span>(result)</pre>
            </div>
        </div>
    </div>

    <script>
        const input = "lee(t(c)o)de)";
        let stack = [];
        let removeIndices = new Set();
        let currentIndex = 0;
        let phase = 'init';
        let autoInterval = null;

        function init() {
            stack = [];
            removeIndices = new Set();
            currentIndex = 0;
            renderString();
            renderStack();
            renderRemove();
            document.getElementById('resultContainer').innerHTML = '<span style="color: #999;">Will appear after Phase 2</span>';
            document.getElementById('scanPhase').classList.remove('active');
            document.getElementById('buildPhase').classList.remove('active');
        }

        function renderString() {
            const container = document.getElementById('stringContainer');
            container.innerHTML = '';
            input.split('').forEach((char, idx) => {
                const box = document.createElement('div');
                box.className = 'array-box';
                box.id = `char-${idx}`;
                box.style.width = '40px';

                if (removeIndices.has(idx)) {
                    box.classList.add('swapping');
                    box.style.textDecoration = 'line-through';
                    box.style.opacity = '0.5';
                }
                if (idx === currentIndex && (phase === 'scanning' || phase === 'building')) {
                    box.classList.add('highlight');
                }

                box.innerHTML = `${char}<span class="index-label">[${idx}]</span>`;
                container.appendChild(box);
            });
        }

        function renderStack() {
            const container = document.getElementById('stackContainer');
            if (stack.length === 0) {
                container.innerHTML = '<span style="color: #999; padding: 10px;">Empty</span>';
                return;
            }
            container.innerHTML = '';
            stack.forEach(idx => {
                const item = document.createElement('div');
                item.className = 'stack-item';
                item.textContent = `( [${idx}]`;
                container.appendChild(item);
            });
        }

        function renderRemove() {
            const container = document.getElementById('removeContainer');
            if (removeIndices.size === 0) {
                container.innerHTML = '<span style="color: #999;">None yet</span>';
            } else {
                container.textContent = `{ ${[...removeIndices].sort((a,b) => a-b).join(', ')} }`;
            }
        }

        function step() {
            if (phase === 'init') {
                phase = 'scanning';
                currentIndex = 0;
                document.getElementById('scanPhase').classList.add('active');
                document.getElementById('statusMessage').textContent =
                    'Phase 1: Scanning for unmatched parentheses...';
            } else if (phase === 'scanning') {
                if (currentIndex >= input.length) {
                    // Add remaining stack to removeIndices
                    while (stack.length > 0) {
                        const idx = stack.pop();
                        removeIndices.add(idx);
                    }
                    renderStack();
                    renderRemove();
                    renderString();

                    phase = 'building';
                    currentIndex = 0;
                    document.getElementById('scanPhase').classList.remove('active');
                    document.getElementById('buildPhase').classList.add('active');
                    document.getElementById('statusMessage').textContent =
                        `Phase 1 complete! Found ${removeIndices.size} invalid parentheses to remove. Starting Phase 2...`;
                    return;
                }

                const char = input[currentIndex];

                if (char === '(') {
                    stack.push(currentIndex);
                    document.getElementById('statusMessage').textContent =
                        `Index ${currentIndex}: Found '(' → Push index ${currentIndex} to stack`;
                } else if (char === ')') {
                    if (stack.length === 0) {
                        removeIndices.add(currentIndex);
                        document.getElementById('statusMessage').textContent =
                            `Index ${currentIndex}: Found ')' but stack empty → Mark for removal`;
                    } else {
                        const matched = stack.pop();
                        document.getElementById('statusMessage').textContent =
                            `Index ${currentIndex}: Found ')' → Matches '(' at index ${matched}, pop from stack`;
                    }
                } else {
                    document.getElementById('statusMessage').textContent =
                        `Index ${currentIndex}: Character '${char}' → Not a parenthesis, skip`;
                }

                renderString();
                renderStack();
                renderRemove();
                currentIndex++;
            } else if (phase === 'building') {
                let result = '';
                for (let i = 0; i < input.length; i++) {
                    if (!removeIndices.has(i)) {
                        result += input[i];
                    }
                }
                document.getElementById('resultContainer').textContent = `"${result}"`;
                document.getElementById('buildPhase').classList.remove('active');
                phase = 'done';
                document.getElementById('statusMessage').textContent =
                    `✅ Done! Removed ${removeIndices.size} characters. Result: "${result}"`;
                document.getElementById('stepBtn').disabled = true;
                stopAuto();
            }
        }

        function toggleAuto() {
            if (autoInterval) {
                stopAuto();
            } else {
                document.getElementById('autoBtn').textContent = 'Pause';
                autoInterval = setInterval(() => {
                    if (phase === 'done') {
                        stopAuto();
                    } else {
                        step();
                    }
                }, 1000);
            }
        }

        function stopAuto() {
            if (autoInterval) {
                clearInterval(autoInterval);
                autoInterval = null;
            }
            document.getElementById('autoBtn').textContent = 'Auto Run';
        }

        function reset() {
            stopAuto();
            phase = 'init';
            document.getElementById('stepBtn').disabled = false;
            document.getElementById('statusMessage').textContent =
                'Click "Step" or "Auto Run" to remove invalid parentheses';
            init();
        }

        init();
    </script>
</body>
</html>