Three ways to sort arrays in PHP_PHP Tutorial

1. Bubble sorting method
Description: Find the largest number, arrange it to the end, and then continue to find

Example:
$arr = array(3,5,-1,0,2);
for($i=0;$i for($j=0;$j If($arr[$j]>$arr[$j+1]){
               $temp = $arr[$j];
               $arr[$j]=$arr[$j+1];
               $arr[$j+1]=$temp;
}
}
}
Comprehension:
3, 5, -1, 0, 2
//Compare starting from the first number and going backwards. If it is larger than the following number, adjust the position with the following number
//The first time, 3 is less than 5, then it remains unchanged
//The second time, 5 is greater than -1, then it becomes
3, -1, 5, 0, 2
//The third time, 5 is greater than 0
3, -1, 0, 5, 2
//The fourth time, 5 is greater than 2
3, -1, 0, 2, 5
This completes an inner loop. At this time, the last number is sorted and will not participate next time
3, -1, 0, 2, 5 The second outer loop begins. The first time: 3 is greater than -1
-1, 3, 0, 2, 5
The second time: 3 is greater than 0
-1, 0, 3, 2, 5
The third time: 3 is greater than 2
-1, 0, 2, 3, 5
This completes the sorting of the next two digits, and so on
-1, 0, 2, 3, 5
2. Selection sorting method Description: First assume that the first number is the smallest number, and then compare the following numbers with it in turn. If the assumed number is not the smallest number, swap its position with the following smallest number
$arr=array(2,1,-1,3,0);
for($i=0;$i $minval = $arr[$i];
$minindex = $i;
for($j=1+$i;$j If($arr[$j]<$minval){
               $minval = $arr[$j];
               $minindex = $j;
}
}
$temp = $arr[$i];
$arr[$i] = $arr[$minindex];
$arr[$minindex] = $temp;
}
Comprehension:
2, 1, -1, 3, 0
//Assume that the first number 2 is the minimum value, and the subsequent numbers are compared with 2 in turn to find the smallest number
Process:
1 is less than 2, then minval=1
-1 is less than 1, then minval=-1
3 is greater than -1, unchanged
0 is greater than -1, unchanged
So now we have found the smallest number in the array, which is -1
Swap the positions of -1 and 2 to complete the sorting of the first number
So now the array becomes
-1, 1, 2, 3, 0
Now the first number -1 is already in order, so it will not participate in the comparison and continue to the next
Now assume minval=1
2 is greater than 1, unchanged
3 is greater than 1, unchanged
0 is less than 1, then minval=0
Now that one cycle is completed, swap the positions of 0 and 1 to complete the sorting of the second number
So now the array becomes
-1, 0, 2, 3, 1
//The following push method is the same as above. . .

3. Insertion sort method description: First assume that the first number in an array is a separate ordered array, and then compare the following number with it [as I grows here, it becomes them]. If If the following number is smaller than the assumed number, move the smaller number back, and finally move that number to the front
$arr=array(2,1,-1,3,0);
for($i=1;$i $insertval=$arr[$i];
$insertindex = $i-1;
While($insertindex>=0 && $insertval<$arr[$insertindex]){
          $arr[$insertindex+1]=$arr[$insertindex];
         $insertindex--;
}
$temp = $arr[$i];
$arr[$insertindex+1]=$insertval;
}
Comprehension:
2, 1, -1, 3, 0
//For the first time, save the number 1 to be inserted as insertval, and then compare insertval with 2. 1 is less than 2, so move 2 back to become the following picture
2, 2, -1, 3, 0
//At this time, there is no number in front of 2, insertindex=0, so the comparison is completed, then insert insertval to the found position. It becomes as shown below
1, 2, -1, 3, 0
//At this time, 1 and 2 become ordered arrays
//The second time, first save the number to be inserted -1 as insertval, and then compare insertval with 2. -1 is less than 2, so move 2 back to become the following picture
1, 2, 2, 3, 0
//At this time, compare insertval with 1. If -1 is less than 1, then move -1 back to become the following picture (this is a process of comparing the number to be inserted with the previous ordered array)
1, 1, 2, 3, 0
//At this point, insertindex has come to an end, so insert insertval at this position
-1, 1, 2, 3, 0
//The following method is as above



Excerpted from Bell’s Technology Blog