/** * @link http://php.net/manual/en/iterator.rewind.php * @return void */ function rewind() { $this->stack = new LinkedStack(); $this->pushLeft($this->root); if (!$this->stack->isEmpty()) { $this->node = $this->stack->last(); $this->key = 0; } }
/** * @link http://php.net/manual/en/iterator.next.php * @return void */ function next() { /** * @var BinaryTree $node */ $node = $this->stack->pop(); $this->pushIfNotNull('right', $node); $this->pushIfNotNull('left', $node); if ($this->stack->isEmpty()) { $this->value = $this->key = null; return; } $this->value = $this->stack->last(); $this->key++; }
private function next_right() { $right = $this->value->right(); if ($right !== null && !$this->stack->isEmpty() && $right === $this->stack->last()) { $this->stack->pop(); $this->next_push($right); } else { $this->next_set(); } }
public function nfx($expr) { $index = 0; $stack = new Stack(); $output = array(); // postfix form of expression, to be passed to pfx() // $expr = trim(strtolower($expr)); $expr = trim($expr); $ops = array('+', '-', '*', '/', '^', '_'); $ops_r = array('+' => 0, '-' => 0, '*' => 0, '/' => 0, '^' => 1); // right-associative operator? $ops_p = array('+' => 0, '-' => 0, '*' => 1, '/' => 1, '_' => 1, '^' => 2); // operator precedence $expecting_op = false; // we use this in syntax-checking the expression // and determining when a - is a negation if (preg_match("/[^\\w\\s+*^\\/()\\.,-]/", $expr, $matches)) { // make sure the characters are all good return $this->trigger("illegal character '{$matches[0]}'"); } while (1) { // 1 Infinite Loop ;) $op = substr($expr, $index, 1); // get the first character at the current index // find out if we're currently at the beginning of a number/variable/function/parenthesis/operand $ex = preg_match('/^([A-Za-z]\\w*\\(?|\\d+(?:\\.\\d*)?|\\.\\d+|\\()/', substr($expr, $index), $match); //=============== if ($op == '-' and !$expecting_op) { // is it a negation instead of a minus? $stack->push('_'); // put a negation on the stack $index++; } elseif ($op == '_') { // we have to explicitly deny this, because it's legal on the stack return $this->trigger("illegal character '_'"); // but not in the input expression //=============== } elseif ((in_array($op, $ops) or $ex) and $expecting_op) { // are we putting an operator on the stack? if ($ex) { // are we expecting an operator but have a number/variable/function/opening parethesis? $op = '*'; $index--; // it's an implicit multiplication } // heart of the algorithm: while ($stack->count > 0 and $o2 = $stack->last() and in_array($o2, $ops) and $ops_r[$op] ? $ops_p[$op] < $ops_p[$o2] : $ops_p[$op] <= $ops_p[$o2]) { $output[] = $stack->pop(); // pop stuff off the stack into the output } // many thanks: http://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail $stack->push($op); // finally put OUR operator onto the stack $index++; $expecting_op = false; //=============== } elseif ($op == ')' and $expecting_op) { // ready to close a parenthesis? while (($o2 = $stack->pop()) != '(') { // pop off the stack back to the last ( if (is_null($o2)) { return $this->trigger("unexpected ')'"); } else { $output[] = $o2; } } if (preg_match("/^([A-Za-z]\\w*)\\(\$/", $stack->last(2), $matches)) { // did we just close a function? $fnn = $matches[1]; // get the function name $arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you) $output[] = $stack->pop(); // pop the function and push onto the output if (in_array($fnn, $this->fb)) { // check the argument count if ($arg_count > 1) { return $this->trigger("too many arguments ({$arg_count} given, 1 expected)"); } } elseif (array_key_exists($fnn, $this->f)) { if ($arg_count != count($this->f[$fnn]['args'])) { return $this->trigger("wrong number of arguments ({$arg_count} given, " . count($this->f[$fnn]['args']) . " expected)"); } } else { // did we somehow push a non-function on the stack? this should never happen return $this->trigger("internal error"); } } $index++; //=============== } elseif ($op == ',' and $expecting_op) { // did we just finish a function argument? while (($o2 = $stack->pop()) != '(') { if (is_null($o2)) { return $this->trigger("unexpected ','"); } else { $output[] = $o2; } // pop the argument expression stuff and push onto the output } // make sure there was a function if (!preg_match("/^([A-Za-z]\\w*)\\(\$/", $stack->last(2), $matches)) { return $this->trigger("unexpected ','"); } $stack->push($stack->pop() + 1); // increment the argument count $stack->push('('); // put the ( back on, we'll need to pop back to it again $index++; $expecting_op = false; //=============== } elseif ($op == '(' and !$expecting_op) { $stack->push('('); // that was easy $index++; $allow_neg = true; //=============== } elseif ($ex and !$expecting_op) { // do we now have a function/variable/number? $expecting_op = true; $val = $match[1]; if (preg_match("/^([A-Za-z]\\w*)\\(\$/", $val, $matches)) { // may be func, or variable w/ implicit multiplication against parentheses... if (in_array($matches[1], $this->fb) or array_key_exists($matches[1], $this->f)) { // it's a func $stack->push($val); $stack->push(1); $stack->push('('); $expecting_op = false; } else { // it's a var w/ implicit multiplication $val = $matches[1]; $output[] = $val; } } else { // it's a plain old var or num $output[] = $val; } $index += strlen($val); //=============== } elseif ($op == ')') { // miscellaneous error checking return $this->trigger("unexpected ')'"); } elseif (in_array($op, $ops) and !$expecting_op) { return $this->trigger("unexpected operator '{$op}'"); } else { // I don't even want to know what you did to get here return $this->trigger("an unexpected error occured"); } if ($index == strlen($expr)) { if (in_array($op, $ops)) { // did we end with an operator? bad. return $this->trigger("operator '{$op}' lacks operand"); } else { break; } } while (substr($expr, $index, 1) == ' ') { // step the index past whitespace (pretty much turns whitespace $index++; // into implicit multiplication if no operator is there) } } while (!is_null($op = $stack->pop())) { // pop everything off the stack and push onto output if ($op == '(') { return $this->trigger("expecting ')'"); } // if there are (s on the stack, ()s were unbalanced $output[] = $op; } return $output; }
} else { echo "stack is empty"; } } public function isEmpty() { if ($this->index == -1) { return true; } else { return false; } } public function first() { echo $this->stackArray[$this->index]; } public function last() { echo $this->stackArray[0]; } } $newStack = new Stack(); $newStack->push(2); $newStack->push(6); $newStack->pop(); $newStack->pop(); $newStack->pop(); $newStack->isEmpty(); $newStack->first(); $newStack->last(); $newStack->getElement(1);
$this->index--; return $element; } echo "There is no element in the quee array"; } public function isEmpty() { if ($this->index == -1) { return true; } else { return false; } } public function first() { return $this->queArray[$this->index]; } public function last() { return $this->queArray[0]; } } $muy = new Stack(array(3, 4, 7)); $myStack = new Stack(); $myStack->push(1); $myStack->push(4); echo $myStack->first(), "<br>"; echo $myStack->last(), "<br>"; echo $myStack->pop(), "<br>"; echo $myStack->pop(), "<br>"; $myStack->pop();