Algorithm Complexity Estimation

Analyze PHP code to estimate time and space complexity.

Complexity Patterns

1. O(n²) Algorithms

// O(n²): Nested loop over same collection
foreach ($items as $i => $item1) {
    foreach ($items as $j => $item2) {
        if ($i !== $j && $item1->matches($item2)) {
            // Comparison
        }
    }
}