PHP 二分查找

答案

  1. function binarySearch($array, $search)
  2. {
  3.     $low = 0;
  4.     $high = count($array) - 1;
  6.     if ($search < $array[$low] || $search > $array[$high]) {
  7.         return false;
  8.     }
  10.     while ($low <= $high) {
  11.         $mid = floor(($high + $low) / 2);
  13.         if ($array[$mid] > $search) {
  14.             $high = $mid - 1;
  15.         } else if ($array[$mid] < $search) {
  16.             $low = $mid + 1;
  17.         } else {
  18.             return $mid;
  19.         }
  20.     }
  22.     return false;
  23. }

时间复杂度：O(log n)