3Sum Closest
<p>Given an integer array <code>nums</code> of length <code>n</code> and an integer <code>target</code>, find three integers in <code>nums</code> such that the sum is closest to <code>target</code>.</p>

<p>Return <em>the sum of the three integers</em>.</p>

<p>You may assume that each input would have exactly one solution.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [-1,2,1,-4], target = 1
<strong>Output:</strong> 2
<strong>Explanation:</strong> The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,0,0], target = 1
<strong>Output:</strong> 0
<strong>Explanation:</strong> The sum that is closest to the target is 0. (0 + 0 + 0 = 0).
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>3 &lt;= nums.length &lt;= 500</code></li>
	<li><code>-1000 &lt;= nums[i] &lt;= 1000</code></li>
	<li><code>-10<sup>4</sup> &lt;= target &lt;= 10<sup>4</sup></code></li>
</ul>
Array; Two Pointers; Sorting
class Solution {
    /**
     * @param int[] $nums
     * @param int $target
     * @return int
     */

    function threeSumClosest($nums, $target) {
        $n = count($nums);
        $closestSum = $nums[0] + $nums[1] + $nums[2];
        $minDiff = abs($closestSum - $target);

        sort($nums);

        for ($i = 0; $i < $n - 2; $i++) {

            $left = $i + 1;
            $right = $n - 1;

            while ($left < $right) {
                $sum = $nums[$i] + $nums[$left] + $nums[$right];
                $diff = abs($sum - $target);

                if ($diff < $minDiff) {
                    $minDiff = $diff;
                    $closestSum = $sum;
                } elseif ($sum < $target) {
                    $left++;
                } elseif ($sum > $target) {
                    $right--;
                } else {
                    return $sum;
                }
            }
        }

        return $closestSum;
    }
}
