Detailed analysis of bubble sort

Bubble sort

For friends who are new to programming and algorithms, the sorting algorithm may not be clear. Next, we will Let’s analyze bubble sorting.

What is the principle of bubble sort?

Traverse an array, during this process, compare the values ​​​​of two adjacent cells: if the former is larger than the latter, the two values ​​​​are swapped. At the end of this process, the maximum value in the array must be placed at the last position.

If the above process is carried out again, it can be determined that the maximum value in the remaining data is placed at the second to last position.

Then continue the above process again, and you can continue to determine that the maximum value in the remaining data is placed at the third to last position.

And so on. . . . .

Illustration:

##The fourth trip1891215 2223The fifth trip91215 182223## Code demonstration:

Original array	18	22	12	15	23	9
First trip	18	22	12	15	9	23
Second trip	18	22	12	9	15	23
The third trip	18	22	9	12	15	23

$arr1 = array(18,22,12,15,23,9);
    $n = count($arr1);
    //控制要进行的躺数
    for($i = 0;$i < $n-1;$i++){
        //在每一趟里面，控制进行比较的次数
        for($k = 0;$k < $n-1-$i;$k++){
            if ($arr1[$k] > $arr1[$k+1]) {
                $temp = $arr1[$k];
                $arr1[$k] = $arr1[$k+1];
                $arr1[$k+1] = $temp;
            }
        }
    }

Finally let’s do To sum up the rules:

1. The number of times to compare pairs from beginning to end and exchange positions is $n-1 times, $n is the total number (array length)

2. Compare the size of two adjacent data every time, and exchange their positions if necessary!

3. The number of comparisons for each trip is one less than the previous trip. The number of comparisons for the first trip is: $n-1

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