Commonly used algorithms in PHP

In the daily PHP development environment, we can use some commonly used PHP algorithms to solve some problems more effectively, or by knowing some algorithms and mastering the core ideas of these algorithms, PHP problems can be easily solved.

1. Bubble sorting

Basic idea:

Sort the array from back to front (reverse order) Perform multiple scans, and when it is found that the order of two adjacent values ​​​​is inconsistent with the rules required for sorting, the two values ​​​​are exchanged. In this way, the smaller (larger) values ​​will gradually move from the back to the front.

//Bubble sorting

<?php
 
  function mysort($arr)
  {
    for($i = 0; $i < count($arr); $i++)
    {
      $isSort = false;
      for ($j=0; $j< count($arr) - $i - 1; $j++) 
      {
        if($arr[$j] < $arr[$j+1])
        {
          $isSort = true;
          $temp = $arr[$j];
          $arr[$j] = $arr[$j+1];
          $arr[$j+1] = $temp ;
        }
      }
      if($isSort)
      {
        break;
      }
    }
    return $arr;
  }
 
  $arr = array(3,1,2);
  var_dump(mysort($arr));
?>

2. Quick sorting

##Basic idea:

In Pick an element (mostly the first one) in the array as the ruler, scan the array once, and sort the elements smaller than the ruler before the ruler, and sort all the elements larger than the ruler after the ruler, and divide each subsequence separately through recursion. into smaller sequences until all sequences are in the same order.

//Quick sort

<?php
  //快速排序
    function quick_sort($arr) 
    {
      //先判断是否需要继续进行
      $length = count($arr);
      if($length <= 1) 
      {
        return $arr;
      }
     
      $base_num = $arr[0];//选择一个标尺 选择第一个元素
 
      //初始化两个数组
      $left_array = array();//小于标尺的
      $right_array = array();//大于标尺的
      for($i=1; $i<$length; $i++) 
      {      //遍历 除了标尺外的所有元素，按照大小关系放入两个数组内
        if($base_num > $arr[$i]) 
        {
          //放入左边数组
          $left_array[] = $arr[$i];
        } 
        else
        {
          //放入右边
          $right_array[] = $arr[$i];
        }
      }
      //再分别对 左边 和 右边的数组进行相同的排序处理方式
      //递归调用这个函数,并记录结果
      $left_array = quick_sort($left_array);
      $right_array = quick_sort($right_array);
      //合并左边 标尺 右边
      return array_merge($left_array, array($base_num), $right_array);
    }
 
    $arr = array(3,1,2);
    var_dump(quick_sort($arr));
 
?>

Three, binary search

##Basic idea

:Assumption data It is sorted in ascending order. For a given value x, comparison starts from the middle position of the sequence. If the current position value is equal to x, the search is successful; if x is less than the current position value, search in the first half of the sequence; The current position value continues to be searched in the second half of the sequence until it is found. (Used when the amount of data is large)

//Binary search

<?php
  //二分查找
  function bin_search($arr,$low,$high,$k)
  {
    if($low <= $high)
    {
      $mid = intval(($low + $high)/2);
      if($arr[$mid] == $k)
      {
        return $mid;
      }
      else if($k < $arr[$mid])
      {
        return bin_search($arr,$low,$mid-1,$k);
      }
      else
      {
        return bin_search($arr,$mid+1,$high,$k);
      }
    }
    return -1;
  }
 
  $arr = array(1,2,3,4,5,6,7,8,9,10);
 
  print(bin_search($arr,0,9,3));
?>

The above are the more commonly used algorithms in PHP development to share with you, hoping to help everyone.

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Examples of common PHP algorithms and data structures

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