PHP Solution for Detecting Duplicate Elements in an Integer Array

Introduction: Detecting duplicate elements in an array requires traversing each element and checking for repeated occurrences.

Problem: Given an integer array nums , return true if any value appears at least twice; otherwise return false .

Example:

Input: nums = [1,2,3,1]
Output: true

Input: nums = [1,2,3,4]
Output: false

Solution: The PHP class Solution implements containsDuplicate($nums) using an associative array $map to store seen elements. The function iterates over $nums , checks if the current element already exists in $map , returns true on a duplicate, otherwise adds the element to $map . After the loop, it returns false .

class Solution {
    /**
     * @param Integer[] $nums
     * @return Boolean
     */
    function containsDuplicate($nums) {
        $map = array();
        foreach ($nums as $n => $i) {
            if (array_key_exists($i, $map)) {
                return true;
            }
            $map[$i] = $n;
        }
        return false;
    }
}

Execution flow: 1) Initialize an empty associative array $map . 2) For each element in $nums , check if it exists in $map . If found, return true . If not, store the element and its index in $map . 3) If the loop finishes without finding duplicates, return false .

Complexity: Time complexity O(n) where n is the number of elements; space complexity O(n) due to the auxiliary associative array.

Conclusion: The optimized PHP solution leverages an associative array for constant‑time lookups, enabling fast and reliable detection of duplicate elements while maintaining stable performance on large datasets.