PHP实现的折半查询算法示例

php;"><?phpheader("Content-type: text/html; charset=utf-8");/* 折半查询算法--不用递归 */function qSort($data = array(), $x = 0){ $startIndex = 0;    // 开始索引 $endIndex = count($data) - 1; // 结束索引 $index = 0; $number = 0;     // 计数器 do{  if($endIndex > $startIndex){   $searchIndex = ceil(($endIndex - $startIndex) / 2);  }else if($endIndex == $startIndex){   $searchIndex = $endIndex;  }else{   $index = -1;   break;  }  $searchIndex += ($startIndex - 1);  echo '检索范围：'.$startIndex.' ~ '.$endIndex.'<br>检索位置：'.$searchIndex.'检索值为：'.$data[$searchIndex];  echo '<br>=======================<br><br>';  if($data[$searchIndex] == $x){   $index = $searchIndex;   break;  }else if($x > $data[$searchIndex]){   $startIndex = $searchIndex + 1;  }else{   $endIndex = $searchIndex - 1;  }  $number++; }while($number < count($data)); return $index;}/* 折半查询算法--使用递归 */function sSort($data, $x, $startIndex, $endIndex){ if($endIndex > $startIndex){  $searchIndex = ceil(($endIndex - $startIndex) / 2); }else if($endIndex == $startIndex){  $searchIndex = $endIndex; }else{  return -1; } $searchIndex += ($startIndex - 1); echo '检索范围：'.$startIndex.' ~ '.$endIndex.'<br>检索位置：'.$searchIndex.'检索值为：'.$data[$searchIndex]; echo '<br>=======================<br><br>'; if($data[$searchIndex] == $x){  return $searchIndex; }else if($x > $data[$searchIndex]){  $startIndex = $searchIndex + 1;  return sSort($data, $x, $startIndex, $endIndex); }else{  $endIndex = $searchIndex - 1;  return sSort($data, $x, $startIndex, $endIndex); }}$data = array(1, 3, 4, 6, 9, 11, 12, 13, 15, 20, 21, 25, 33, 34, 35, 39, 41, 44);$index = qSort($data, 11);      // 不用递归的排序方法$index = sSort($data, 11, 0, count($data) - 1); // 使用递归的排序方法echo '结果：'.$index;