在javascript中使用堆栈的前缀计算器

class Stack {
  constructor() {
    this.items = [];
  }

  push(item) {
    this.items.push(item);
  }

  pop() {
    if (this.isEmpty()) {
      throw new Error("Stack is empty");
    }
    return this.items.pop();
  }

  peek() {
    if (this.isEmpty()) {
      throw new Error("Stack is empty");
    }
    return this.items[this.items.length - 1];
  }

  isEmpty() {
    return this.items.length === 0;
  }
}

function prefixCalculator(expression) {
  const stack = new Stack();
  const operators = ["+", "-", "*", "/"]; // 支持的运算符

  for (let i = expression.length - 1; i >= 0; i--) {
    const token = expression[i];

    if (!operators.includes(token)) {
      // 操作数，压入堆栈
      stack.push(parseFloat(token));
    } else {
      // 运算符，从堆栈中弹出两个操作数进行计算
      const operand1 = stack.pop();
      const operand2 = stack.pop();

      let result;
      switch (token) {
        case "+":
          result = operand1 + operand2;
          break;
        case "-":
          result = operand1 - operand2;
          break;
        case "*":
          result = operand1 * operand2;
          break;
        case "/":
          result = operand1 / operand2;
          break;
      }

      // 将计算结果压入堆栈
      stack.push(result);
    }
  }

  // 返回最终计算结果
  return stack.pop();
}

const expression = ["+", "*", "2", "3", "4"]; // + * 2 3 4 的前缀表达式
const result = prefixCalculator(expression);
console.log(result); // 输出 14