题解 | #四则运算#

<?php

class Scanner {
    /** @var resource */
    protected $in;

    /**
     * Scanner constructor.
     * @param $uri "php://input", "file:///D:/Users/mingz/CLionProjects/nowcoder/huawei/core.txt"
     */
    public function __construct(/* string */$uri = "php://stdin") {
        $this->in = fopen($uri, 'r');
    }

    private static function isBlank($c) {
        return strncmp($c, " ", 1) == 0 || strncmp($c, "\t", 1) == 0
            || strncmp($c, "\r", 1) == 0 || strncmp($c, "\n", 1) == 0;
    }

    /**
     * Get a word from resource $this->in, char by char
     * @return string
     */
    private function getWord() {
        $ch = fgetc($this->in);
        for (; !feof($this->in); $ch = fgetc($this->in)) {
            if (!self::isBlank($ch)) {break;}
        }
        // $at = ftell($this->in);
        $word = "";
        for (; !feof($this->in); ) {
            if (self::isBlank($ch)) {
                break;
            } else {
                $word .= $ch;
            }
            $ch = fgetc($this->in);
        }
        return $word;
    }

    private static function atoi($s) {
        $num = 0;
        $i = 0;
        for (; isset($s[$i]); $i += 1) {
            if (!self::isBlank($s[$i])) {break;}
        }
        $codeMinus = ord("-");
        $negative = false;
        if (ord($s[$i]) == $codeMinus) {
            $negative = true;
            $i += 1;
        }
        $codeDot = ord(".");
        for (; isset($s[$i]); $i += 1) {
            $code = ord($s[$i]);
            if (48 <= $code && $code < 58) {
                $num = 10 * $num + ($code - 48);
            } elseif ($code == $codeDot) {
                break;
            }
            if ($num > PHP_INT_MAX) {
                throw new OutOfRangeException("Integer out of range: ".PHP_INT_MAX);
            }
        }
        if ($negative) {$num = 0 - $num;}
        return $num;
    }

    public function nextInt() {
        $nextWord = "";
        for (;;) {
            $nextWord = $this->getWord();
            if (is_numeric($nextWord)) {break;}
        }
        return self::atoi($nextWord);
    }

    public function nextLine() {
        $line = fgets($this->in);
        return rtrim($line, "\r\n");
    }

    public function next() {return $this->getWord();}
    public function hasNext() {
        if (feof($this->in)) {
            return false;
        }
        $pos = ftell($this->in);
        $bytesRead = fread($this->in, 2);
        if (false == $bytesRead) {
            return false;
        }
        fseek($this->in, $pos);
        return !empty(rtrim($bytesRead, "\r\n"));
    }
    public function __destruct() {fclose($this->in);}

}
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);
    }
}

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));
        }
    }
}