题解 | #四则运算#

import java.util.*;

public class Main { public static void main(String[] args) {

	Scanner sc = new Scanner(System.in);
	String str = sc.next();
	str = str.replace('{', '(');
	str = str.replace('[', '(');
	str = str.replace('}', ')');
	str = str.replace(']', ')');

	System.out.println(solve(str));

}

static int calc(char op, int right, int left) {
	switch (op) {
	case '+':
		return left + right;
	case '-':
		return left - right;
	case '*':
		return left * right;
	case '/':
		return left / right;
	default:
		return 0;
	}
}

static int solve(String str) {
	Stack<Integer> sOutNum = new Stack<Integer>();
	Stack<Character> sOutOp = new Stack<Character>();
	sOutNum.push(0);
	sOutOp.push('+');
	for (int i = 0; i < str.length(); i++) {
		char c = str.charAt(i);
		if (Character.isDigit(c)) {
			// 前面是数字
			if (i > 0 && Character.isDigit(str.charAt(i - 1))) {
				sOutNum.push(sOutNum.pop() * 10 + (c - '0'));
			} else if (i > 0 && str.charAt(i - 1) == '-') {
				sOutOp.pop();
				sOutNum.push(-1 * (c - '0'));
				if(i!=1)
				{
					sOutOp.push('+');
				}
			} else {
				sOutNum.push(c - '0');
			}
		} else {
			if( (c == '+' || c == '-') && (i!=0)){

				if (sOutOp.isEmpty() == false) {
					int temp = calc(sOutOp.pop(), sOutNum.pop(), sOutNum.pop());
					sOutNum.push(temp);
					sOutOp.push(c);
				} else {
					sOutOp.push(c);
				}
			} else if (c == '*' || c == '/') {
				char prev = sOutOp.peek();
				if (prev == '*' || prev == '/') {
					int temp = calc(sOutOp.pop(), sOutNum.pop(), sOutNum.pop());
					sOutNum.push(temp);
					sOutOp.push(c);
				} else {
					sOutOp.push(c);
				}

			} else if (c == '(') {

				int leftBrac = 1;
				int j = i + 1;
				while (leftBrac > 0) {
					if (str.charAt(j) == ')') {
						leftBrac--;
					} else if (str.charAt(j) == '(') {
						leftBrac++;
					}
					j++;
				}
				int num = solve(str.substring(i + 1, j - 1));
				if(i==1 && str.charAt(i-1)=='-')
				{
					num = num*(-1);
					sOutNum.push(num);
				}
				if(i>1 && str.charAt(i-1)=='-')
				{
					sOutOp.pop();
					num = num*(-1);
					sOutNum.push(num);
					sOutOp.push('+');
				}else
				{
					sOutNum.push(num);
				}
				
				i = j - 1;
				continue;
			}else
			{
				sOutOp.push(c);
			}

		}
	}

	while (sOutOp.isEmpty() == false) {
		int res2 = calc(sOutOp.pop(), sOutNum.pop(), sOutNum.pop());
		sOutNum.push(res2);
	}
	return sOutNum.pop();
}

}