Detailed explanation of various classic algorithms implemented in PHP

This article mainly shares with you detailed explanations of various classic algorithms implemented in PHP. Interested friends can make a reference

##

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270

<?    //--------------------  // 基本数据结构算法 //--------------------  //二分查找（数组里查找某个元素）  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, $k);             }         }         return -1;     }     //顺序查找（数组里查找某个元素）  function  seq_sch($array, $n,  $k){         $array[$n] =  $k;         for($i=0;  $i<$n; $i++){             if( $array[$i]==$k){                 break;             }         }         if ($i<$n){             return  $i;         }else{             return -1;         }     }     //线性表的删除（数组中实现）  function delete_array_element($array , $i)    {            $len =  count($array);             for ($j= $i; $j<$len; $j ++){                    $array[$j] = $array [$j+1];            }            array_pop ($array);            return $array ;    }    //冒泡排序（数组排序）  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 $array;    }    //快速排序（数组排序）  function quick_sort($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), $right_arr);    }    //------------------------  // PHP内置字符串函数实现  //------------------------  //字符串长度  function strlen ($str)    {            if ($str == &#39;&#39; ) return 0;            $count =  0;            while (1){                    if ( $str[$count] != NULL){                             $count++;                            continue;                    }else{                            break;                    }            }            return $count;    }    //截取子串  function substr($str, $start,  $length=NULL)    {            if ($str== &#39;&#39; || $start>strlen($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 $substr;    }    //字符串翻转  function strrev($str)    {            if ($str == &#39;&#39;) return 0 ;            for ($i=(strlen($str)- 1); $i>=0; $i --){                    $rev_str .= $str[$i ];            }            return $rev_str;    }    //字符串比较  function strcmp($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;    }    //查找字符串  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 $i;            }            return false ;    }    //字符串替换  function str_replace($substr , $newsubstr, $str)    {             $m = strlen($str);            $n = strlen($substr );            $x = strlen($newsubstr );            if (strchr($str, $substr ) == false) return false;            for ( $i=0; $i<=($m- $n+1); $i++){                     $i = strchr($str,  $substr);                    $str = str_delete ($str, $i, $n);                    $str = str_insert($str,  $i, $newstr);            }            return $str ;    }    //--------------------  // 自实现字符串处理函数 //--------------------  //插入一段字符串  function str_insert($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 $str ;    }    //删除一段字符串  function str_delete($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 $str;    }    //复制字符串  function strcpy($s1, $s2 )    {            if (strlen($s1)==NULL || !isset( $s2)) return;            for ($i=0 ; $i<strlen($s1);  $i++){                    $s2[] = $s1 [$i];            }            return $s2;    }    //连接字符串  function strcat($s1 , $s2)    {            if (!isset($s1) || !isset( $s2)) return;            $newstr = $s1 ;            for($i=0; $i <count($s); $i ++){                    $newstr .= $st[$i ];            }            return $newsstr;    }    //简单编码函数（与php_decode函数对应）  function php_encode($str)    {            if ( $str==&#39;&#39; && strlen( $str)>128) return false;            for( $i=0; $i<strlen ($str); $i++){                     $c = ord($str[$i ]);                    if ($c>31 && $c <107) $c += 20 ;                    if ($c>106 && $c <127) $c -= 75 ;                    $word = chr($c );                    $s .= $word;            }             return $s;     }    //简单解码函数（与php_encode函数对应）  function php_decode($str)    {            if ( $str==&#39;&#39; && strlen($str )>128) return false;            for( $i=0; $i<strlen ($str); $i++){                    $c  = ord($word);                    if ( $c>106 && $c<127 ) $c = $c-20;                    if ($c>31 && $c< 107) $c = $c+75 ;                    $word = chr( $c);                    $s .= $word ;            }             return $s;     }    //简单加密函数（与php_decrypt函数对应）  function php_encrypt($str)    {             $encrypt_key = &#39;abcdefghijklmnopqrstuvwxyz1234567890&#39;;             $decrypt_key = &#39;ngzqtcobmuhelkpdawxfyivrsj2468021359&#39;;            if ( strlen($str) == 0) return  false;            for ($i=0;  $i<strlen($str); $i ++){                    for ($j=0; $j <strlen($encrypt_key); $j ++){                            if ($str[$i] == $encrypt_key [$j]){                                    $enstr .=  $decrypt_key[$j];                                    break;                            }                    }            }            return $enstr;    }    //简单解密函数（与php_encrypt函数对应）  function php_decrypt($str)    {             $encrypt_key = &#39;abcdefghijklmnopqrstuvwxyz1234567890&#39;;             $decrypt_key = &#39;ngzqtcobmuhelkpdawxfyivrsj2468021359&#39;;            if ( strlen($str) == 0) return  false;            for ($i=0;  $i<strlen($str); $i ++){                    for ($j=0; $j <strlen($decrypt_key); $j ++){                            if ($str[$i] == $decrypt_key [$j]){                                    $enstr .=  $encrypt_key[$j];                                    break;                            }                    }            }            return $enstr;    }    ?>

Copy after login

php algorithm questions

Simple PHP algorithm questions (with expansion)

php algorithm example sharing

The above is the detailed content of Detailed explanation of various classic algorithms implemented in PHP. For more information, please follow other related articles on the PHP Chinese website!