Basic data structure and PHP built-in function implementation

Basic data structure and PHP built-in function implementation_PHP tutorial

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Release： 2016-07-21 14:57:30

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Binary search function

//Binary search (find an element in an array)
function bin_sch($array, $low, $high, $k){
if ($low <= $high){
$mid = intval(($low+$high)/2);
if ($array[$mid] == $k){
return $mid;
}elseif ($k < $array[$mid]){
return bin_sch($array, $low, $mid-1, $k);
}else{
return bin_sch( $array, $mid+1, $high, $k);
}
}
return -1;
}

Implementation of sequential search function

//Sequential search (search for an element in the array)
function seq_sch($array, $n, $k){
$array[$n] = $k;
for($ i=0; $i<$n; $i++){
if($array[$i]==$k){
break;
}
}
if ($ i<$n){
return $i;
}else{
return -1;
}
}
Implementation of deletion function of linear table

//Deletion of linear tables (implemented in arrays)
function delete_array_element($array, $i)
{
$len = count($array);
for ($j=$i; $j<$len; $j++){
$array[$j] = $array[$j+1];
}
array_pop($array);
return $array;
}
Implementation of bubble sort function:

//Bubble sort (array sort)
function bubble_sort($array)
{
$count = count($ array);
if ($count <= 0) return false;

for($i=0; $i<$count; $i++){
for($j=$ count-1; $j>$i; $j--){
if ($array[$j] < $array[$j-1]){
$tmp = $array[$j ];
$array[$j] = $array[$j-1];
$array[$j-1] = $tmp;
}
}
}
return $array;
}
Quick sort function implementation

//Quick sort (array sort)
function quicksort($array) {
if (count($array) <= 1) return $array;

$key = $array[0];
$left_arr = array();
$right_arr = array();

for ($i=1; $iif ($array[$i] <= $key)
$left_arr[] = $array[$i ];
else
$right_arr[] = $array[$i];
}

$left_arr = quicksort($left_arr);
$right_arr = quicksort($right_arr );

return array_merge($left_arr, array($key), $right_arr);
}

PHP built-in string function implementation

//-- -----------------------
// PHP built-in string function implementation
//------------ ------------

//String length
function strlen($str)
{
if ($str == '') return 0 ;

$count = 0;
while (1){
if ($str[$count] != NULL){
$count++;
continue;
}else{
break;
}
}
return $count;
}

//Intercept substring function to implement

function substr($str, $start, $length=NULL)
{
if ($str=='' || $start>strlen($str)) return;
if (($length! =NULL) && ($start>0) && ($length>strlen($str)-$start)) return;
if (($length!=NULL) && ($start<0) && ($length> ;strlen($str)+$start)) return;

if ($length == NULL) $length = (strlen($str) - $start);
if ($start < 0){
for ($i=(strlen($str)+$start); $i<(strlen($str)+$start+$length); $i++) {
$substr .= $ str[$i];
}
}

if ($length > 0){
for ($i=$start; $i<($start+$length); $i++) {