PHP four basic Algorithm code example _php tutorial

PHP four basic algorithms: bubbling, selection, insertion and quick Sort method
Many people say that the algorithm is the core of the program, a program is better than poor, the key is the merits of the program algorithm. As a primary phper, although it is seldom exposed to algorithmic aspects of things. But for the bubble sort, insert sort, choose Sort, quick sort four basic algorithms, I think still have to master. Here are my own understanding of the four methods to analyze it again.
Requirements: Using bubble sort method, quick sorting method, selecting Sort method, inserting sorting method to sort the values in the following array in order from small to the next.
$arr (1,43,54,62,21,66,32,78,36,76,39);

1. Bubble Sorting method
* Thinking Analysis: The law, as its name, is like bubbling, each time from the array to take a maximum number out.
* For example: 2,4,1//The First bubble that pops up is 4
* 2,1,4//The Second bubble that pops up is 2
* 1,2,4//The end is like this

* Code implementation:
Copy the Code code as follows:
$arr =array (1,43,54,62,21,66,32,78,36,76,39);
function Getpao ($arr)
{
$len =count ($arr);
Set an empty array to receive the bubbling
The layer loop controls the number of rounds that need to bubble
for ($i =1; $i < $len; $i + +)
{//This layer loop is used to control the number of times a number needs to be compared per round
for ($k =0; $k < $len-$i; $k + +)
{
if ($arr [$k]> $arr [$k +1])
{
$tmp = $arr [$k +1];
$arr [$k +1]= $arr [$k];
$arr [$k]= $tmp;
}
}
}
return $arr;
}

2. Select sorting:
Choose a sorting method: Select a corresponding element each time, and then place it at the specified location
Copy code code as follows:
function Select_sort ($arr) {
//Realize the idea of double loop completion, outer control wheel count, current minimum value. The number of comparisons of the inner control
//$i The position of the current minimum value, the element to be involved in the comparison
for ($i =0, $len =count ($arr); $i < $len-1; $i + +) {
//First assume the position of the smallest value
$p = $i ; The
//$j currently need to compare with which elements, $i behind.
for ($j = $i +1; $j < $len; $j + +) {
//$arr [$p] is the currently known minimum value
if ($arr [$p] > $arr [$j]) {
//compare, find smaller, record the position of the minimum value; And at the next comparison, the
//should be compared with a known minimum value.
$p = $j;
}
}
//The location of the current minimum value has been determined and saved to $p.
//If the position of the minimum value is found to be different from the current assumed position $i, the position is interchangeable
if ($p! = $i) {
$tmp = $arr [$p];
$arr [$p] = $arr [$i];
$arr [$i] = $tm P
}
}
//Return final result
return $arr;
}

3. Insert Sort method
Insert Sort idea: Inserts the element that will be sorted into the specified position of the array that has assumed the sort number. The
copy Code code is as follows:
function Insert_sort ($arr) {
//distinguish which part is already sorted
//Which part is not sorted
// Find one of the elements that need to be sorted
//This element is starting with the second element, and the last element is the element that needs to be sorted
//The loop can be used to flag the
//i loop control each element that needs to be inserted, once the element that needs to be inserted is controlled,
// Indirectly has divided the array into 2 parts, the subscript is smaller than the current (left), is a sorted sequence
for ($i =1, $len =count ($arr); $i < $len; $i + +) {
//Get the element values that are currently being compared.
$tmp = $arr [$i];
//Inner loop control compares and inserts
for ($j = $i-1; $j >=0; $j-) {
//$arr [$i];//the element that needs to be inserted; $arr [$j];//the element to compare
if ($tmp < $arr [$j]) {
//find the inserted element to be small, swap position
//swap the element behind it with the previous element
$arr [$j +1] = $arr [$j];
//Set the previous number to the number currently required to be swapped
$arr [$j] = $tmp;
} else {
//If you encounter an element that does not need to be moved
//Because the array is already sorted, the preceding one does not need to be compared again.
break;
}
}
}
//Inserts this element into an already sorted sequence.
//return
return $arr;
}

4. Quick Sort Method
Copy the Code code as follows:
function Quick_sort ($arr) {
Determine if you need to proceed
$length = count ($arr);
if ($length <= 1) {
return $arr;
}
If there is no return, the number of elements in the array is 1 extra and needs to be sorted
Select a ruler
Select the first element
$base _num = $arr [0];
Iterates through all elements except the ruler, and fits into two arrays in relation to size
Initialize two arrays
$left _array = Array ();//less than the ruler
$right _array = Array ();//greater than the ruler
for ($i =1; $i < $length; $i + +) {
if ($base _num > $arr [$i]) {
Put in the left array
$left _array[] = $arr [$i];
} else {
Put it on the right
$right _array[] = $arr [$i];
}
}
The same sort method for the left and right arrays, respectively.
Call this function recursively and record the result
$left _array = Quick_sort ($left _array);
$right _array = Quick_sort ($right _array);
Merge left ruler right
Return Array_merge ($left _array, Array ($base _num), $right _array);
}

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