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<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>N-Queens Problem Visualizer</title>
<script src="https://cdn.tailwindcss.com"></script>
<link href="https://unpkg.com/aos@2.3.1/dist/aos.css" rel="stylesheet">
<script src="https://unpkg.com/aos@2.3.1/dist/aos.js"></script>
<script src="https://cdn.jsdelivr.net/npm/feather-icons/dist/feather.min.js"></script>
<script src="https://unpkg.com/feather-icons"></script>
<style>
.chess-board {
display: grid;
aspect-ratio: 1/1;
border: 2px solid #333;
}
.chess-cell {
display: flex;
justify-content: center;
align-items: center;
position: relative;
}
.queen {
color: #dc2626;
font-size: 80%;
}
.conflict {
background-color: rgba(239, 68, 68, 0.3) !important;
}
.solution-node {
transition: all 0.3s ease;
cursor: pointer;
}
.solution-node:hover {
transform: scale(1.05);
}
.tree-container {
max-height: 60vh;
overflow-y: auto;
}
.active-solution {
border: 2px solid #3b82f6;
box-shadow: 0 0 10px rgba(59, 130, 246, 0.5);
}
</style>
</head>
<body class="bg-gray-50 min-h-screen">
<div class="container mx-auto px-4 py-8">
<header class="text-center mb-8" data-aos="fade-down">
<h1 class="text-3xl md:text-4xl font-bold text-gray-800 mb-2">N-Queens Problem Visualizer</h1>
<p class="text-gray-600">Place N queens on an N×N chessboard so that no two queens threaten each other</p>
</header>
<div class="grid grid-cols-1 lg:grid-cols-2 gap-8">
<!-- Left Column: Controls and Chessboard -->
<div class="space-y-6">
<div class="bg-white rounded-lg shadow-md p-6" data-aos="fade-right">
<h2 class="text-xl font-semibold mb-4 flex items-center">
<i data-feather="sliders" class="mr-2"></i> Configuration
</h2>
<div class="mb-4">
<label class="block text-sm font-medium text-gray-700 mb-2">Board Size (N)</label>
<div class="flex items-center space-x-4">
<input type="range" min="1" max="8" value="4" class="w-full" id="boardSizeSlider">
<span class="text-lg font-medium w-8 text-center" id="boardSizeValue">4</span>
</div>
</div>
<div class="flex space-x-3">
<button id="solveBtn" class="flex-1 bg-blue-600 hover:bg-blue-700 text-white py-2 px-4 rounded-md flex items-center justify-center">
<i data-feather="play" class="mr-2"></i> Solve
</button>
<button id="resetBtn" class="flex-1 bg-gray-200 hover:bg-gray-300 text-gray-800 py-2 px-4 rounded-md flex items-center justify-center">
<i data-feather="refresh-cw" class="mr-2"></i> Reset
</button>
</div>
</div>
<div class="bg-white rounded-lg shadow-md p-6" data-aos="fade-right" data-aos-delay="100">
<h2 class="text-xl font-semibold mb-4 flex items-center">
<i data-feather="grid" class="mr-2"></i> Chessboard
</h2>
<div class="flex justify-center">
<div id="chessboardContainer" class="w-full max-w-md"></div>
</div>
</div>
</div>
<!-- Right Column: Solutions and Space Tree -->
<div class="space-y-6">
<div class="bg-white rounded-lg shadow-md p-6" data-aos="fade-left">
<h2 class="text-xl font-semibold mb-4 flex items-center">
<i data-feather="list" class="mr-2"></i> Solutions
<span id="solutionsCount" class="ml-2 bg-blue-100 text-blue-800 text-xs font-medium px-2.5 py-0.5 rounded">0 found</span>
</h2>
<div id="solutionsContainer" class="grid grid-cols-2 sm:grid-cols-3 gap-3 max-h-60 overflow-y-auto"></div>
</div>
<div class="bg-white rounded-lg shadow-md p-6" data-aos="fade-left" data-aos-delay="100">
<h2 class="text-xl font-semibold mb-4 flex items-center">
<i data-feather="git-branch" class="mr-2"></i> Search Space Tree
</h2>
<div id="treeContainer" class="tree-container bg-gray-100 p-4 rounded-md">
<div id="treeVisualization" class="relative"></div>
</div>
</div>
</div>
</div>
</div>
<script>
// Initialize libraries
document.addEventListener('DOMContentLoaded', function() {
AOS.init();
feather.replace();
// Initialize the chessboard
const boardSizeSlider = document.getElementById('boardSizeSlider');
const boardSizeValue = document.getElementById('boardSizeValue');
const chessboardContainer = document.getElementById('chessboardContainer');
const solutionsContainer = document.getElementById('solutionsContainer');
const solutionsCount = document.getElementById('solutionsCount');
const treeVisualization = document.getElementById('treeVisualization');
const solveBtn = document.getElementById('solveBtn');
const resetBtn = document.getElementById('resetBtn');
let currentSize = 4;
let solutions = [];
let currentSolutionIndex = -1;
// Create the initial chessboard
createChessboard(currentSize);
// Event listeners
boardSizeSlider.addEventListener('input', function() {
currentSize = parseInt(this.value);
boardSizeValue.textContent = currentSize;
createChessboard(currentSize);
clearSolutions();
});
solveBtn.addEventListener('click', function() {
solveNQueens(currentSize);
});
resetBtn.addEventListener('click', function() {
createChessboard(currentSize);
clearSolutions();
});
function createChessboard(size) {
chessboardContainer.innerHTML = '';
const board = document.createElement('div');
board.className = 'chess-board';
board.style.gridTemplateColumns = `repeat(${size}, 1fr)`;
board.style.gridTemplateRows = `repeat(${size}, 1fr)`;
for (let row = 0; row < size; row++) {
for (let col = 0; col < size; col++) {
const cell = document.createElement('div');
cell.className = `chess-cell ${(row + col) % 2 === 0 ? 'bg-gray-100' : 'bg-gray-300'}`;
cell.dataset.row = row;
cell.dataset.col = col;
board.appendChild(cell);
}
}
chessboardContainer.appendChild(board);
}
function solveNQueens(n) {
solutions = [];
currentSolutionIndex = -1;
clearSolutions();
// Solve using backtracking
const board = Array(n).fill().map(() => Array(n).fill(0));
solveNQueensUtil(board, 0, n);
// Display solutions count
solutionsCount.textContent = `${solutions.length} found`;
// Display solutions
if (solutions.length > 0) {
displaySolutions();
displaySearchTree(n);
showSolution(0); // Show first solution by default
} else {
solutionsContainer.innerHTML = '<p class="text-gray-500 text-center col-span-full">No solutions found</p>';
treeVisualization.innerHTML = '<p class="text-gray-500 text-center">No search tree to display</p>';
}
}
function solveNQueensUtil(board, col, n) {
if (col >= n) {
// Found a solution
const solution = [];
for (let i = 0; i < n; i++) {
for (let j = 0; j < n; j++) {
if (board[i][j] === 1) {
solution.push(j);
}
}
}
solutions.push(solution);
return;
}
for (let i = 0; i < n; i++) {
if (isSafe(board, i, col, n)) {
board[i][col] = 1;
solveNQueensUtil(board, col + 1, n);
board[i][col] = 0; // backtrack
}
}
}
function isSafe(board, row, col, n) {
// Check row on left side
for (let i = 0; i < col; i++) {
if (board[row][i] === 1) return false;
}
// Check upper diagonal on left side
for (let i = row, j = col; i >= 0 && j >= 0; i--, j--) {
if (board[i][j] === 1) return false;
}
// Check lower diagonal on left side
for (let i = row, j = col; i < n && j >= 0; i++, j--) {
if (board[i][j] === 1) return false;
}
return true;
}
function displaySolutions() {
solutionsContainer.innerHTML = '';
solutions.forEach((solution, index) => {
const solutionElement = document.createElement('div');
solutionElement.className = 'solution-node bg-white border rounded-md p-2 text-center cursor-pointer';
solutionElement.innerHTML = `
<div class="text-sm font-medium">Solution ${index + 1}</div>
<div class="text-xs text-gray-500">[${solution.join(', ')}]</div>
`;
solutionElement.addEventListener('click', () => {
showSolution(index);
});
solutionsContainer.appendChild(solutionElement);
});
}
function showSolution(index) {
// Remove active class from all solutions
document.querySelectorAll('.solution-node').forEach(node => {
node.classList.remove('active-solution', 'bg-blue-50');
});
// Add active class to selected solution
document.querySelectorAll('.solution-node')[index].classList.add('active-solution', 'bg-blue-50');
currentSolutionIndex = index;
renderBoardWithSolution(solutions[index]);
}
function renderBoardWithSolution(solution) {
const cells = document.querySelectorAll('.chess-cell');
const n = solution.length;
// Clear the board
cells.forEach(cell => {
cell.innerHTML = '';
cell.classList.remove('conflict');
});
// Place queens
for (let col = 0; col < n; col++) {
const row = solution[col];
const cellIndex = row * n + col;
if (cells[cellIndex]) {
cells[cellIndex].innerHTML = '<i data-feather="circle" class="queen"></i>';
}
}
feather.replace();
}
function displaySearchTree(n) {
treeVisualization.innerHTML = '';
// Create a simplified visualization of the search space
const treeContainer = document.createElement('div');
treeContainer.className = 'space-y-4';
// Add title
const title = document.createElement('div');
title.className = 'text-sm font-medium text-gray-700';
title.textContent = `Search space for ${n}-queens problem`;
treeContainer.appendChild(title);
// Add info about the search
const info = document.createElement('div');
info.className = 'text-xs text-gray-500';
info.innerHTML = `
<p>• The algorithm uses backtracking to explore possible queen placements</p>
<p>• Each level represents a column where a queen is being placed</p>
<p>• Valid placements continue to the next level (column)</p>
<p>• Invalid placements cause backtracking to previous levels</p>
`;
treeContainer.appendChild(info);
// Add visualization of the search process
const visual = document.createElement('div');
visual.className = 'bg-blue-50 p-3 rounded-md mt-2';
const visualContent = document.createElement('div');
visualContent.className = 'text-xs';
if (n <= 4) {
visualContent.innerHTML = `
<p class="font-medium mb-1">Search Process:</p>
<p>1. Start with column 0, try all rows</p>
<p>2. For each valid placement, move to next column</p>
<p>3. When a solution is found, record it and backtrack</p>
<p>4. Continue until all possibilities are explored</p>
`;
} else {
visualContent.innerHTML = `
<p class="font-medium mb-1">Search Process (simplified):</p>
<p>The search tree for ${n}-queens is too large to display in detail.</p>
<p>The algorithm explored ${Math.pow(n, n)} possible placements</p>
<p>but used constraints to prune invalid branches early.</p>
`;
}
visual.appendChild(visualContent);
treeContainer.appendChild(visual);
treeVisualization.appendChild(treeContainer);
}
function clearSolutions() {
solutions = [];
currentSolutionIndex = -1;
solutionsContainer.innerHTML = '';
solutionsCount.textContent = '0 found';
treeVisualization.innerHTML = '<p class="text-gray-500 text-center">Solve to see search tree</p>';
// Clear any queens from the board
const cells = document.querySelectorAll('.chess-cell');
cells.forEach(cell => {
cell.innerHTML = '';
cell.classList.remove('conflict');
});
}
});
</script>
</body>
</html>
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