PHP array learning uses bubble algorithm to sort elements in ascending order!

In the previous article "PHP Array Learning: Returning All Common Factors and the Greatest Common Factor between Given Two Numbers", we introduced the use of array methods to return given two integers a and b All common factors and the greatest common factor method. This time we will study PHP arrays and introduce how to use PHP to implement bubble sorting and how to use the bubble algorithm to sort array elements in ascending order.

First of all, let’s understandWhat is the bubble algorithm (bubble sort)?

Bubble Sort (Bubble Sort) is because the smaller elements will slowly "float" to the top of the sequence through exchange (arranged in ascending or descending order), just like the carbon dioxide bubbles in carbonated drinks Eventually it will float to the top, hence the name "bubble sort".

Idea:

• Compare two adjacent elements, if the conditions are met (the first is greater than the second, or the first is greater than the two small), exchange them, otherwise they won’t move.

• Then compare the next two adjacent elements, and then exchange them if the conditions are met, otherwise they will remain unchanged.

• Just do the same thing for every pair of adjacent elements, starting with the first pair at the beginning and ending with the last pair at the end. The last element should be the largest (smallest) number.

• Continue the loop operation in sequence, and the final element will be fixed at the bottom.

We use the bubble algorithm to sort the array elements in ascending order:

There is such an array:

$arr = array('23','4','0','3','2','24','20');

The array has 7 elements , because it is to implement ascending sorting, that is, sorting from small to large, so the execution steps are:

First round of loop:

• The first element 23 and the second element 4 ratio, because 23 is greater than 4, so a swap operation is performed

• The second element (23 at this time) is compared with the third element 0, because 23 is greater than 0, so a swap operation is performed Operation---23 becomes the third element

• The ratio of the third element (23 at this time) to the fourth element is still greater than 3, perform the exchange operation--- 23 becomes the fourth element

• The fourth element (23 at this time) is still greater than the fifth element 2, perform the exchange operation---23 becomes The fifth element

• The fifth element (23 at this time) is compared with the sixth element 24. Because 23 is less than 24, no exchange operation is performed-the sixth element is still 24

• The sixth element (24 at this time) is compared with the seventh element 20. Because 24 is greater than 200, a swap operation is performed---24 becomes the seventh element

After a round of cyclic comparison, the largest number will sink to the bottom. Small numbers gradually emerge upward.

The array elements at this time are: 4, 0, 3, 2, 23, 20, 24

Second round of loop:

• First The ratio of the first element 4 and the second element 0, because 4 is greater than 0, so the exchange operation is performed---4 becomes the second element

• The second element (this time is 4) Compare with the third element 3, because 4 is greater than 3, so perform the exchange operation---4 becomes the third element

• The third element (this time is 4 ) is still greater than the fourth element 2, perform a swap operation---4 becomes the fourth element

• The fourth element (this time is 4) and the fifth The ratio of elements to 23 is because 4 is less than 23, so no exchange operation is performed---the fifth element is still 23

• The fifth element (23 at this time) and the sixth element 20 ratio, because 23 is greater than 20, perform the exchange operation - 23 becomes the sixth element

• The sixth element (this time is 23) and the seventh element 24 ratio, Less than, so no exchange operation is performed - the seventh element is still 24

At this time, the array elements are: 0, 3, 2, 4, 20, 23, 24

....

And so on, the final array elements are: 0, 2, 3, 4, 20, 23, 24

Let's take a look at the implementation method:

 $arr[$j+1]) {
 
				$data      = $arr[$i]; 
				$arr[$i]   = $arr[$j+1];
				$arr[$j+1] = $data; 
			}
		}
	}
 
	return $arr;
}
echo "
";
print_r(BubbleSort($arr));
Copy after login

Output result:

Okay, that’s all. If you want to know anything else, you can click this. → →php video tutorial

Finally, I would like to recommend a free video tutorial on PHP arrays: PHP function array array function video explanation, come and learn!

The above is the detailed content of PHP array learning uses bubble algorithm to sort elements in ascending order!. For more information, please follow other related articles on the PHP Chinese website!