Example analysis of PHP classic algorithm

This article mainly and everyone to share the PHP classic algorithm example analysis, hope to help everyone.

<

?        --------------------///Basic data structure algorithm//--------------------//Two-point lookup (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, $k);   }} return-1;       }//Order lookup (find an element in an array) function Seq_sch ($array, $n, $k) {$array [$n] = $k;  for ($i = 0; $i < $n;           $i + +) {if ($array [$i]== $k) {break;       }} if ($i < $n) {return $i;       }else{return-1;           }}//The deletion of a linear table (implemented in an array) function delete_array_element ($array, $i) {$len = count ($array);          for ($j = $i; $j < $len; $j + +) {$array [$j] = $array [$j +1];          } array_pop ($array); Return $arRay;          }//Bubble sort (array sort) function Bubble_sort ($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 $array;          }//Quick sort (array sort) function Quick_sort ($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), $right _arr);  }//------------------------//php built-in string function implementation//------------------------//String length function strlen ($str) {if          ($str = = ") return 0;          $count = 0;                          while (1) {if ($str [$count]! = NULL) {$count + +;                  Continue                  }else{break;  }} return $count;          }//Intercept substring function substr ($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 $substr;          }//String rollover function Strrev ($STR) {if ($str = = ") return 0;          for ($i = (strlen ($str)-1), $i >=0; $i-) {$rev _str. = $str [$i];  } return $rev _str;          }//string comparison function strcmp ($s 1, $s 2) {if (strlen ($s 1) < strlen ($s 2)) return-1;          if (strlen ($s 1) > strlen ($s 2)) return 1;             for ($i =0; $i <strlen ($s 1); $i + +) {if ($s 1[$i] = = $s 2[$i]) {             Continue                  }else{return false;  }} return 0;          }//Find String 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 $i;  } return false;          }//String substitution function Str_replace ($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 $STR; }//--------------------//self-implementing string processing function//--------------------//Insert a String function Str_insert ($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 $str;  }//Delete a string function Str_delete ($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 $str;          }//Copy string function strcpy ($s 1, $s 2) {if (strlen ($s 1) ==null | |!isset ($s 2)) return;  for ($i =0; $i <strlen ($s 1);          $i + +) {$s 2[] = $s 1 [$i];  } return $s 2;          }//connection string function strcat ($s 1, $s 2) {if (!isset ($s 1) | |!isset ($s 2)) return;          $newstr = $s 1; for ($i =0; $i <count ($s); $i + +) {$newstr. = $st [$i];  } return $NEWSSTR; }//Simple-coded function (corresponding to Php_decode function) functions Php_encode ($STR) {if ($str = = ' && strlen ($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 $s; }//Simple decoding function (corresponding to Php_encode function) functions Php_decode ($STR) {if ($str = = ' && strlen ($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 $s; }//Simple cryptographic functions (with the Php_decrypt functioncorresponding) function Php_encrypt ($str) {$encrypt _key = ' abcdefghijklmnopqrstuvwxyz1234567890 ';          $decrypt _key = ' ngzqtcobmuhelkpdawxfyivrsj2468021359 ';          if (strlen ($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 $enstr; }//Simple decryption function (corresponding to the Php_encrypt function) functions Php_decrypt ($str) {$encrypt _key = ' abcdefghijklmnopqrstuvwxyz123456789           0 ';          $decrypt _key = ' ngzqtcobmuhelkpdawxfyivrsj2468021359 ';          if (strlen ($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; }?>