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This article mainly introduces the basic algorithm collection of PHP, which has certain reference value. Now I share it with everyone. Friends in need can refer to it
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, $k); } } return -1; }
This method is for index arrays and the value is sorted from small to large
Associative arrays are not applicable, the array sorting method is inconsistent or there is no sorting, please modify the if condition accordingly to increase the sorting Wait
function seq_sch($array, $n, $k){ $array[$n] = $k; for($i=0; $i<$n; $i++){ if( $array[$i]==$k){ break; } } if ($i<$n){ return $i; }else{ return -1; } } 此方法适用于索引数组并且$n = count($array);
Simplified enhanced version
function seq_sch($array, $k){ $y = $m = 'no'; foreach($array as $i => $v){ if($v == $k){ if($i == 'no'){$m = 'yes'}//防止key = no $y = $i; break; } } if ($y != 'no' || $m == 'yes'){ return $y; }else{ return -1; } } 此方法适用于所有一维数组
function delete_array_element($array , $i){ $len = count($array); for ($j=$i; $j<$len; $j++){ $array[$j] = $array [$j+1]; } array_pop ($array); return $array ; }
$i specifies the deletion parameter position
function bubble_sort($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]){ //引用第三变量进项数组交换 $tmp = $array[$j]; $array[$j] = $array[ $j-1]; $array [$j-1] = $tmp; } } } return $array; }
function quick_sort($array ) { if (count($array) <= 1) return $array; $key = $array [0]; $left_arr = array(); $right_arr = array(); for ($i= 1; $i<count($array ); $i++){ if ($array[ $i] <= $key) $left_arr [] = $array[$i]; else $right_arr[] = $array[$i]; } $left_arr = quick_sort($left_arr); $right_arr = quick_sort($right_arr); return array_merge($left_arr , array($key), $right_arr); }
function strlen ($str){ if ($str == '' ) return 0; $count = 0; while (1){ if ($str[$count] != NULL){ $count++; continue; }else{ break; } } return $count; }
while (1) 1 represents a constant expression, which will never equal 0. Therefore, the loop will continue to execute. Unless you set a break or similar statement to jump out of the loop, the loop will terminate.
$str[count] PHP is a weakly typed language. You can use subscripts to read the corresponding parameters at the corresponding position
function substr($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++) { $substr .= $str[$i]; } } if ($length < 0){ for ($i =$start; $i<(strlen($str)+$length); $i++) { $substr .= $str[$i ]; } } return $substr;
}
function strrev($str){ if ($str == '') return 0 ; for ($i=(strlen($str)- 1); $i>=0; $i --){ $rev_str .= $str[$i ]; } return $rev_str; }
function strcmp($s1, $s2){ if (strlen($s1) < strlen($s2)) return -1 ; if (strlen($s1) > strlen( $s2)) return 1; for ($i=0; $i<strlen($s1); $i++){ if ($s1[$i] == $s2[$i]){ continue; }else{ return false; } } return 0; }
function strstr($str, $substr){ $m = strlen($str); $n = strlen($substr); if ($m < $n) return false ; for($i=0; $i<=($m-$n+1); $i++){ $sub = substr($str, $i, $n); if (strcmp($sub, $substr) == 0) return $i; } return false ; }
strcmp(
substr) String comparison method If you don’t want to use the comparison method, please add a for loop
function str_replace($substr, $newsubstr, $str){ $m = strlen($str); $n = strlen($substr); $x = strlen($newsubstr); if (strchr($str, $substr) == false) return false; $str_new = $str for ($i=0; $i<=($m-$n+1); $i++){ $i = strchr($str, $substr); $str = str_delete($str_new, $i, $n); $str = str_insert($str_new, $i, $newstr); } return $str_new; }
strchr() function searches for the first occurrence of a string in another string.
This function is an alias of the strstr() function.
function str_insert($str, $i , $substr) { for($j=0 ; $j<$i; $j++){ $startstr .= $str[$j]; } for ($j=$i; $j <strlen($str); $j++){ $laststr .= $str[$j ]; } $str = $startstr.$substr.$laststr; return $str ; }
function str_delete($str, $i, $j){ for ( $c=0; $c<$i; $c++){ $startstr .= $str [$c]; } for ($c=( $i+$j); $c<strlen ($str); $c++){ $laststr .= $str[$c]; } $str = $startstr.$laststr; return $str; }
function strcpy($s1, $s2){ if (strlen($s1)==NULL || !isset($s2)) return; for ($i=0; $i<strlen($s1); $i++){ $s2[] = $s1[$i]; } return $s2; }
function strcat($s1 ,$s2){ if (!isset($s1) || !isset( $s2)) return; $newstr = $s1 ; for($i=0; $i<strlen($s2); $i++){ $newstr .= $s2[$i]; } return $newstr; }
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