justhomework/SoftwareDesign/Lab3/Lab3-1-2_Calculator4490_v4/cal.cpp

#include "cal.h"
QString inToPost(QString infix) {
  std::stack<char> stack;
  char current = 0; //读入的字符
  QString postfix;  //写入后缀表达式的字符串

  std::map<char, int> priority; //运算符号优先级表
  priority['+'] = 0;
  priority['-'] = 0;
  priority['*'] = 1;
  priority['/'] = 1;
  priority['^'] = 2;

  for (int i = 0; i < infix.length(); ++i) //逐个读取中缀表达式字符串中的字符
  {
    current = infix[i].toLatin1();
    if (isdigit(current)) //如果是数字直接输出
    {
      postfix.push_back(current);
      continue;
    }
    switch (current) {
    case '+':
    case '-':
    case '*':
    case '/':
    case '^':
      // postfix.push_back('#');
      if (i >
          0) //如果运算符的前一项不是右括号则说明前一个数字输入完毕，用#标识前面几个字符组成一个数字
      {
        if (infix[i - 1] != ')')
          postfix.push_back('#');
        /*if(infix[i-1].isDigit())
            postfix.push_back('#');
        else
            throw "expression is illegality";*/
      } else
        postfix.push_back('#');
      if (!stack
               .empty()) //比较目前符号与栈顶符号优先级，低于则出栈，并输出字符串
      {
        char tempTop = stack.top();
        while (tempTop != '(' && priority[current] <= priority[tempTop]) {
          stack.pop();
          postfix.push_back(tempTop);
          if (stack.empty())
            break;
          tempTop = stack.top();
        }
      }
      stack.push(
          current); //符号全部出栈或者遇到了'('或者大于栈顶符号的优先级，将新符号压入栈中
      break;
    case '.':
      postfix.push_back(current);
      break;
    case '%':
      postfix.push_back(current);
      break;
    case '(':
      stack.push(current); //左括号直接入栈
      break;
    case ')':
      postfix.push_back('#'); //右括号说明前方数字输入完成，标识一下
      char tempTop;
      tempTop = stack.top();
      while (tempTop != '(') //直到栈顶元素是左括号才停止循环
      {
        stack.pop();
        postfix.push_back(tempTop);
        tempTop = stack.top();
      }
      stack.pop();
      break;
    default:
      throw "expression has illegality character";
      break;
    }
  }
  if (infix[infix.size() - 1] != ')') {
    if (infix[infix.size() - 1].isDigit())
      postfix.push_back('#');
    else
      throw "expression is illegality";
  }
  while (!stack.empty()) {
    char tempOut = stack.top();
    stack.pop();
    postfix.push_back(tempOut);
  }
  return postfix;
}

double compute(QString s) {
  std::stack<double> stack;
  QString str;
  double curr;

  double temNum1;
  double temNum2;
  for (auto i = s.begin(); i != s.end(); i++) {
    if ((*i).isDigit()) {
      str.push_back(*i);
      continue;
    }
    switch ((*i).toLatin1()) {
    case '+':
      temNum1 = stack.top();
      stack.pop();
      temNum2 = stack.top();
      stack.pop();
      stack.push(temNum2 + temNum1);
      break;
    case '-':
      temNum1 = stack.top();
      stack.pop();
      temNum2 = stack.top();
      stack.pop();
      stack.push(temNum2 - temNum1);
      break;
    case '*':
      temNum1 = stack.top();
      stack.pop();
      temNum2 = stack.top();
      stack.pop();
      stack.push(temNum2 * temNum1);
      break;
    case '/':
      temNum1 = stack.top();
      stack.pop();
      temNum2 = stack.top();
      stack.pop();
      stack.push(temNum2 / temNum1);
      break;
    case '^':
      temNum1 = stack.top();
      stack.pop();
      temNum2 = stack.top();
      stack.pop();
      stack.push(pow(temNum2, temNum1));
      break;
    case '.':
      str.push_back(*i);
      break;
    case '#':
      curr = str.toDouble(); //字符串转换为浮点型
      str.clear();
      stack.push(curr);
      break;
    case '%':
      curr = stack.top();
      stack.pop();
      curr *= 0.01;
      stack.push(curr);
      break;
    default:
      throw "expression has illegality character";
      break;
    }
  }
  curr = stack.top();
  return curr;
}