Common php Algorithms and time complexity

This article provides a detailed analysis of common php Algorithms and time complexity. For more information, see sort by order of magnitude. Common time complexity: constant order O (1), logarithm order O (log2n), linear order O (n), linear logarithm order O (nlog2n), square order O (n2 ), cubic order O (n3)

The code is as follows:

// Binary search O (log2n)
Function erfen ($ a, $ l, $ h, $ f ){
If ($ l> $ h) {return false ;}
$ M = intval ($ l + $ h)/2 );
If ($ a [$ m] ==$ f ){
Return $ m;
} Elseif ($ f <$ a [$ m]) {
Return erfen ($ a, $ l, $ M-1, $ f );
} Else {
Return erfen ($ a, $ m + 1, $ h, $ f );
}

}
$ A = array (88,100 );
Var_dump (erfen ($ a, 0, 5, 1 ));
// Traverse tree O (log2n)
Function bianli ($ p ){
$ A = array ();
Foreach (glob ($ p. '/*') as $ f ){
If (is_dir ($ f )){
$ A = array_merge ($ a, bianli ($ f ));
} Else {
$ A [] = $ f;
}
}
Return $;
}
// Factorial O (log2n)
Function jc ($ n ){
If ($ n <= 1 ){
Return 1;
} Else {
Return $ n * jc ($ n-1 );
}
}
// Quickly search for O (n * log2 (n ))
Function kuaisu ($ ){
$ C = count ($ );
If ($ c <= 1) {return $ ;}
$ L = $ r = array ();
For ($ I = 1; $ I <$ c; $ I ++ ){
If ($ a [$ I] <$ a [0]) {
$ L [] = $ a [$ I];
} Else {
$ R [] = $ a [$ I];
}
}
$ L = kuaisu ($ l );
$ R = kuaisu ($ r );
Return array_merge ($ l, array ($ a [0]), $ r );
}
// Insert sort O (N * N)
Function charu ($ ){
$ C = count ($ );
For ($ I = 1; $ I <$ c; $ I ++ ){
$ T = $ a [$ I];
For ($ j = $ I; $ j> 0 & $ a [$ j-1]> $ t; $ j --){
$ A [$ j] = $ a [$ j-1];
}
$ A [$ j] = $ t;
}
Return $;
}
// Select sorting O (N * N)
Function xuanze ($ ){
$ C = count ($ );
For ($ I = 0; $ I <$ c; $ I ++ ){
For ($ j = $ I + 1; $ j <$ c; $ j ++ ){
If ($ a [$ I]> $ a [$ j]) {
$ T = $ a [$ j];
$ A [$ j] = $ a [$ I];
$ A [$ I] = $ t;
}
}
}
Return $;
}
// Bubble sort O (N * N)
Function maopao ($ ){
$ C = count ($ );
For ($ I = 0; $ I <$ c; $ I ++ ){
For ($ j = $ C-1; $ j> $ I; $ j --){
If ($ a [$ j] <$ a [$ j-1]) {
$ T = $ a [$ j-1];
$ A [$ j-1] = $ a [$ j];
$ A [$ j] = $ t;
}
}
}
Return $;
}

The code is as follows:

/**
* Arrangement and combination
* Use the binary method to select a combination. for example, if you select 5 or 3, you only need to set 3 to 1, therefore, we can obtain 10 combinations, including 01101, 11100, 00111, and 10011.
*
* @ Param: array to be arranged $ arr
* @ Param minimum number $ min_size
* @ Return: a new array combination that meets the conditions
*/
Function plzh ($ arr, $ size = 5 ){
$ Len = count ($ arr );
$ Max = pow (2, $ len );
$ Min = pow (2, $ size)-1;
$ R_arr = array ();
For ($ I = $ min; $ I <$ max; $ I ++ ){
$ Count = 0;
$ T_arr = array ();
For ($ j = 0; $ j <$ len; $ j ++ ){
$ A = pow (2, $ j );
$ T = $ I & $;
If ($ t = $ ){
$ T_arr [] = $ arr [$ j];
$ Count ++;
}
}
If ($ count = $ size ){
$ R_arr [] = $ t_arr;
}
}
Return $ r_arr;
}

$ Pl = pl (array (1, 2, 3, 4, 5, 6, 7), 5 );
Var_dump ($ pl );