编程
过程: 用class 模拟链表实现堆栈 .:p
完整测试程序地址: http://test.hightman.net/stack/stack_05.php
在表单里可输入: (3+5)/2 之类的表达试，支持 ()+-/*
以下为全部代码
data = $value;
    $newnode->next = $stack;
    $stack = $newnode;
}
function pop(&$stack, &$value)
{
    if ($stack != null)
    {
    $value = $stack->data;
    $stack = $stack->next;
    }
    else
    $value = -1;
}
function is_operator($op)
{
    return strchr(+-*/(), $op);
}
function privority($op)
{
    if ($op == ')' || $op == '(')
    return 1;
    else if ($op == '+' || $op == '-')
    return 2;
    else if ($op == '*' || $op == '/')
    return 3;
    else
    return 0;
}
function two_result($op, $n1, $n2)
{
    switch ($op)
    {
    case '+' : return ($n2 + $n1);
    case '-' : return ($n2 - $n1);
    case '*' : return ($n2 * $n1);
    case '/' : return ($n2 / $n1);
    }
}
// main program
$expression = trim($_post['expression']);
if (empty($expression))
{
    print
please input the inorder expression :
__eof__;
    exit();
}$stack_op = null;
$stack_on = null;
$n1 = $n2 = 0;
$op = '';
$len = strlen($expression);
$tmp = '';
for ($i = 0; $i {
    if (is_operator($expression[$i]))
    {
    $tmp = trim($tmp);
    if (!empty($tmp))
    {
        push($stack_on, $tmp);
        $tmp = '';
    }
    if ($expression[$i] == '(' || empty($stack_op))
        push($stack_op, $expression[$i]);
    else if ($expression[$i] == ')')
    {
        while ($stack_op->data != '(')
        {
        pop($stack_on, $n1);
        pop($stack_on, $n2);
        pop($stack_op, $op);
        push($stack_on, two_result($op, $n1, $n2));
        }
        pop($stack_op, $op); // pop the '('
    }
    else {
        while (privority($expression[$i]) data))
        {
        pop($stack_on, $n1);
        pop($stack_on, $n2);
        pop($stack_op, $op);
        push($stack_on, two_result($op, $n1, $n2));
        }
        push($stack_op, $expression[$i]);
    }
    }
    else
    $tmp .= $expression[$i];
}
$tmp = trim($tmp);
if (!empty($tmp))
{
    push($stack_on, $tmp);
    $tmp = '';
}
while (!empty($stack_op))
{
    pop($stack_op, $op);
    pop($stack_on, $n1);
    pop($stack_on, $n2);
    push($stack_on, two_result($op, $n1, $n2));
}
$result = 0;
pop($stack_on, $result);
print     the expression { $expression } result is '$result'
if you wan to try again, please input the inorder expression :
__eof__;?>