PHP Quick Sorting principle and implementation method analysis, PHP sorting principle Implementation _php Tutorial

PHP Quick Sort principle and implementation method analysis, the PHP sorting principle realizes

In this paper, a quick ordering method for PHP is described. Share to everyone for your reference, as follows:

<?php$n = Array (' 13 ', ' 14 ', ' 55 ', ' 10 ', ' 54 ', ' 2 ', ' 79 ', ' 106 ', ' 89 ', ' 90 ', ' 22 ', ' 60 ', ' 111 ', ' 77777 ', '-110 ', '-10 ', ' 123 ') ; function partition ($n, $left, $right) {  global $n;  $pivot = $n [$left];  $lo = $left;  $hi = $right +1;  while ($lo +1!= $hi) {    if ($n [$lo +1]< $pivot)      $lo + +;    else if ($n [$hi -1]> $pivot)      $hi-;    else{      $t = $n [$lo +1];      $n [$lo +1]= $n [$hi-1];      $n [$hi -1]= $t;      $lo + +;      $hi--;    }  }  $n [$left]= $n [$lo];  $n [$lo]= $pivot;  return $lo;} function quicksort ($n, $left, $right) {  global $n;  $DP = 0;  if ($left < $right) {     $dp =partition ($n, $left, $right);     Quicksort ($n, $left, $DP-1);     Quicksort ($n, $DP +1, $right);  }} Quicksort ($n, 0,sizeof ($n)-1);p Rint_r ($n);? >

A quick sort is an improvement to the bubbling sort. Its basic idea is: by a lying sort will be sorted into two separate parts of the data, one part of all the data is smaller than the other part of all the data, and then the second method of the two parts of the data are quickly sorted, the entire sorting process can be recursive, so as to achieve the entire data into an ordered sequence.

Suppose the array to be sorted is a[1] ... A[n], the first arbitrary selection of data (usually the first data) as the key data, and then put all the smaller than its number in front of it, all the larger than its number is placed behind it, this process is called a lie fast sort. A quick-sort algorithm for lying down is:

1), set two variables I, J, the beginning of the sorting i:=1,j:=n;
2), with the first array element as the key data, assigns the value to X, namely x:=a[1];
3), starting from J forward search, that is, after the start of the forward search (j:=j-1), find the first value less than X, the two exchange;
4), from I start backward search, that is, to start backward search (i:=i+1), find the first value greater than X, the two exchange;
5), repeat the 3rd and 4 steps until i=j;

A quick sort is a recursive invocation of this process--dividing the data sequence by a 49 midpoint, a similar quick ordering of the previous and subsequent parts, and a quick ordering of all the data sequences, and finally turning this data series into an ordered sequence

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