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

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2022-05-07 07:48:50 +00:00
#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;
}