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Sharing the method of implementing half query algorithm in PHP

黄舟
黄舟Original
2017-10-09 09:05:181046browse

This article mainly introduces the half query algorithm implemented in PHP, and analyzes the algorithm operation steps and usage methods of PHP using recursive and non-recursive half query in the form of a complete example. Friends who need it can refer to it

The example in this article describes the half query algorithm implemented in PHP. Share it with everyone for your reference, the details are as follows:

What is the half query algorithm? Describe yourself in Baidu with specific words. Directly upload the code:


<?php
header("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 &#39;检索范围:&#39;.$startIndex.&#39; ~ &#39;.$endIndex.&#39;<br>检索位置:&#39;.$searchIndex.&#39;检索值为:&#39;.$data[$searchIndex];
  echo &#39;<br>=======================<br><br>&#39;;
  if($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 &#39;检索范围:&#39;.$startIndex.&#39; ~ &#39;.$endIndex.&#39;<br>检索位置:&#39;.$searchIndex.&#39;检索值为:&#39;.$data[$searchIndex];
 echo &#39;<br>=======================<br><br>&#39;;
 if($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($data) - 1); // 使用递归的排序方法
echo &#39;结果:&#39;.$index;

Running result:

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