Three sorting methods of arrays in PHP. 1. Bubble sorting method description: Locate the maximum number, arrange it to the end, and continue to find the example: $ arrarray (,-, 2); for ($ i0; $ icount ($ arr)-1; $ I ++) {for ($ j0; $ jcount ($ arr)-1-$ I 1. Bubble sort
Note: find the maximum number, arrange it to the last side, and continue to find it.
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;
}
}
}
Understanding:
3, 5,-1, 0, 2
// Compare the values starting from the first number.
// For the first time, 3 is less than 5, so it remains unchanged
// For the second time, if 5 is greater than-1
3 ,-,
// 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
So far, an internal loop is completed, and the last number is sorted.
3,-, the second external loop starts the first time: 3 is greater than-1
-1, 3, 0, 2, 5
Second: 3 is greater than 0
-1, 0, 3, 2, 5
Third time: 3 is greater than 2
-1, 0, 2, 3, 5
So far, the sorting of the next two digits is completed, and so on.
-1, 0, 2, 3, 5
II. sorting method: assume that the first number is the smallest number, and then compare the subsequent number with it in sequence. if the number is not the smallest, change it to the 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;
}
Understanding:
2, 1,-1, 3, 0
// Assume that the first number 2 is the minimum value, and the number after it is compared with 2 in sequence to find the minimum number
Process:
1 is less than 2, so minval = 1
-1 is less than 1, then minval =-1
3 is greater than-1, unchanged
0 is greater than-1, unchanged
Now, the minimum number in the array is-1.
Change the positions of-1 and 2 to sort the first number.
Now the array is changed
-1, 1, 2, 3, 0
Now the first number-1 is in order, so we do not participate in the comparison.
Now suppose minval = 1
2 is greater than 1, unchanged
3 is greater than 1, unchanged
If 0 is less than 1, minval = 0
Now a loop is completed, and the second number is sorted by changing the positions 0 and 1.
Now the array is changed
-1, 0, 2, 3, 1
// The following method is the same as above...
III. Insert sorting method description: assume that the first number in an array is a separate ordered array, and then the next number and it [here with its I increase, it turns into them.] if the number behind is smaller than the assumed number, move the smaller number to the beginning.
$ 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;
}
Understanding:
2, 1,-1, 3, 0
// For the first time, first save the number 1 to be inserted as insertval, and then compare insertval with 2. 1 is smaller than 2, so move 2 back to the following figure.
2, 2,-1, 3, 0
// At this time, there is no number before 2, insertindex = 0, so the comparison is complete, then insert insertval to the position found. Change to as shown in figure
1, 2,-1, 3, 0
// At this time, 1 or 2 is an ordered array
// For the second time, first save the number to be inserted-1 as insertval, then compare insertval with 2,-1 is smaller than 2, so move 2 back, as shown in
1, 2, 3, 0
// At this time, compare insertval with 1. if-1 is smaller than 1, move-1 back and change it to an example (this is a process of comparing the number to be inserted with the preceding ordered array)
1, 1, 2, 3, 0
// At this time, insertindex is in the beginning, so insert insertval into this position
-1, 1, 2, 3, 0
// The Push method is as follows:
From Bell's technical blog
Explain description: find the maximum number, arrange it to the end, and continue to find the example: $ arr = array (,-, 2); for ($ I = 0; $ icount ($ arr)-1; $ I ++) {for ($ j = 0; $ jcount ($ arr)-1-$ I...
