<?php  /**   *  查找   *   **/  // 顺序查找  function normal_search($arrData,$val) {      $len = count($arrData);      if($len == 0) return -1;      for($i = 0;$i < $len; $i++ ) {          echo "find No.",$i + 1," value = ",$arrData[$i]," is = ",$val,"? <br/>";          // 找到了          if($arrData[$i] == $val) return $i;      }      return -1;  }     // 测试顺序查找  $arrData = array(4,51,6,73,2,5,9,33,50,3,4,6,1,4,67);  echo normal_search($arrData,6),"<br/>";  echo normal_search($arrData,66),"<br/>";     // 二分法查找(针对有序的列进行查找)  function binary_search($arrData,$val) {      $len = count($arrData);      if($len == 0) return -1;         $start = 0;      $end   = $len - 1;         while($start <= $end) {          $middle = intval(($start + $end)/2);          echo "start = ",$start," end = ",$end," middle = ",$middle,"<br/>";          if($arrData[$middle] == $val) {              return $middle;          } elseif ($arrData[$middle] > $val) {              $end = $middle - 1 ;          } elseif ($arrData[$middle] < $val) {              $start = $middle + 1;          }      }      return -1;  }     // 测试一下二分法查找  $arrData = array(1,2,3,4,5,7,8,9,11,23,56,100,104,578,1000);  echo binary_search($arrData,578),"<br/>";  echo binary_search($arrData,66),"<br/>";