Fast sequencing of algorithm research

Quick Sort (Quicksort) is an improvement to the bubbling sort. by C. A. R. Hoare was introduced in 1962. Its basic idea is: by a trip to sort the data to be sorted into two separate parts, one part of all the data is smaller than the other part of all the data, and then the two parts of the data are quickly sorted by this method, the entire sorting process can be recursive, so as to achieve the entire data into an ordered sequence.
The above is from Baidu Encyclopedia.
Worst time complexity:
O (n two times);
The best time complexity:
O (n);
The basic idea of quick sorting
1. Decomposition:
In D[I...J...N] 's data, find a benchmark point d[j], divide the data into about two parts,
Left equals d[i...j-1]
Right equals D[J+1...N]
2. Solving
The recursive call division function solves the two data division of the left and right interval.
3. Merge the left and right two sorted data
Visible fast sorting algorithm time complexity is equal to the time spent dividing.
Let's talk about the key second part of the solution

Partitioning steps
Data D[low...high];
① set two variable i,j, pointing to the low and high of the data, respectively. Take any of these data as Datum pivot.
② move J from right to left to find data that is smaller than pivot, and then assign the data that J points to i,d[i]=d[j]
Move I from left to right, look for data larger than pivot, and then assign the data I pointed to J when I find it. D[j]=d[i];
And so on constantly exchanging direction, know i=j time to stop. This time I's position is where the datum pivot is located.

Let's go through this process through the data.
Quotations are not well described in words. So I use strokes in the book to come out.
I can't write well. Do not spray. ^.^


Code written by PHP

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Functionquick_sort (& $array, $x, $y) {     $i = $x;     $j = $y;      $key = $array [$x];//datum     while ($i! = $j) {         //$j--Find a value smaller than the benchmark $key         while ($i < $j && $array [$ J] >= $key) {             $j--;         }        //  if ($i < $j)           $array [$i] = $array [$j];         //$i + + finds values larger than the benchmark $key         while ($i < $j && $array [$i] < = $key) {             $i ++;         }        //if ($i < $j)           $array [$j] = $array [$i];    }     $array [$i] = $key;     if ($x < $i-1) data         quick_sort of  //left interval ($ Array, $x, $i-1),     if ($y > $i + 1)//right-interval data          Quick_sort ($array, $i +1, $y);}

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Fast sequencing of algorithm research