[PHP知识库]HJ50 四则运算

https://www.nowcoder.com/ta/huawei? ?HJ50

输入:

(56-2)/(4+2)
1+2+3+4
3+2*{1+2*[-4/(8-6)+7]}

* index.php

<?php

include "Scanner.php";
include "HJ50.php";

class Solution {
    public static function main() {
        $sc = new Scanner("php://stdin");
        // $sc = new Scanner("./input/input.txt");
        $solution = new HJ50();
        while ($sc->hasNext()) {
            $line = $sc->nextLine();
            printf("%s\n", $solution->compute($line));
        }
    }
}

Solution::main();

* Scanner.php

* HJ50.php

<?php


class HJ50
{
    const ORD_0 = 48;

    private static function isdigit($c): bool {
        $code = ord($c[0]);
        return 48 <= $code && $code < 58;
    }

    private static function isOpenBrace($c) :bool {
        return $c == '{' || $c == '[' || $c == '(';
    }

    private static function isCloseBrace($c) : bool {
        return $c == '}' || $c == ']' || $c == ')';
    }

    /**
     * @param $data string
     * @param $len int
     * @param $pos int
     * @return int
     */
    private static function _compute(string $data, int $len, int &$pos): int
    {
        $num = 0;
        $op = '+';
        $st = array(); // stack

        while ($pos < $len) {

            if (self::isOpenBrace($data[$pos])) {
                $pos += 1;
                $num = self::_compute($data, $len, $pos);
            }
            while ($pos < $len && self::isdigit($data[$pos])) {
                $num = $num * 10 + ord($data[$pos]) - self::ORD_0;
                $pos += 1;
            }
            switch ($op) {
                case '+': array_push($st, $num); break;
                case '-': array_push($st, -$num); break;
                case '*':
                    $tmp = array_pop($st);
                    $tmp *= $num;
                    array_push($st, $tmp);
                    break;
                case '/':
                    $tmp = array_pop($st);
                    $tmp = floor($tmp / $num);
                    array_push($st, $tmp);
                    break;
                default:
            }
            $num = 0;
            $op = $data[$pos];
            if (self::isCloseBrace($data[$pos])) {
                $pos += 1;
                break;
            }
            $pos += 1;
        }
        $sum = 0;
        while (!empty($st)) {
            $sum += array_pop($st);
        }
        return $sum;
    }

    /**
     * @param $data
     * @return int
     */
    public function compute($data): int
    {
        $pos = 0;
        return self::_compute($data, strlen($data), $pos);
    }
}