逆波兰表达式计算器

参考文档：http://blog.csdn.net/geniusluzh/article/details/8192780

参考文档：http://baike.baidu.com/view/552648.htm

 (Owed by: 春夜喜雨 http://blog.csdn.net/chunyexiyu)
逆波兰表达式计算器：逆波兰表达式的生成，参考上面的文档，写了一份样例代码出来：

解析形如：

(CODE1 + CODE2) * CODE3，解析为：CODE1 CODE2 + CODE3 *，支持计算 1+(2+3)*2 等混合运算结果 

QString GetWholeWord(const QString& sInput, const int nStartPos, int& nOutEndPos)
{
QString sWord;
nOutEndPos = nStartPos;
for (int i = nStartPos; i < sInput.length(); i++)
{
QChar ch = sInput.at(i);
if ((ch >= '0' && ch <= '9')
|| (ch >= 'a' && ch <= 'z')
|| (ch >= 'A' && ch <= 'Z')
|| (ch == '.'))
{
sWord += ch;
nOutEndPos = i;
}
else
{
break;
}
}
return sWord;
};

QString AnlysisExpr(QString sInputExpr)
{
// 获取逆波兰表达式
QStack<QString> stackMain;
QStack<QString> stackOper;
for (int i = 0; i < sInputExpr.length(); i++)
{
QChar ch = sInputExpr[i];
if (ch == ' ')
{ // 空格
continue;
}
else if (ch == '(')
{ // 左括号
stackOper.push(QString(ch));
}
else if (ch == ')')
{ // 右括号
while (!stackOper.empty())
{
QString chPop = stackOper.pop();
if (chPop != "(")
{
stackMain.push(chPop);
}
else
{
break;
}
}
}
else if ((ch >= '0' && ch <= '9')
|| (ch >= 'a' && ch <= 'z')
|| (ch >= 'A' && ch <= 'Z')
|| (ch == '.'))
{ // 数字或字符
stackMain.push(GetWholeWord(sInputExpr, i, i));
}
else if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{ // 操作符
if (stackOper.empty())
{ //
stackOper.push(QString(ch));
}
else
{ // 出栈直到遇到优先小于等于的
QString chTemp = stackOper.top();
while (((ch == '+' || ch == '-') && (chTemp == "*" || chTemp == "/"))
                    || ((ch == '+' || ch == '-') && (chTemp == "+" || chTemp == "-"))
                    || ((ch == '*' || ch == '/') && (chTemp == "*" || chTemp == "/")))
{
stackMain.push(stackOper.pop());
if (stackOper.size() > 0)
chTemp = stackOper.top();
else
break;
}
stackOper.push(QString(ch));
}
}
}
while (!stackOper.empty())
{
QString chPop = stackOper.pop();
stackMain.push(chPop);
}

QString sText;
QStack<QString> stackCalc;
while (!stackMain.empty())
{
QString chPop = stackMain.pop();
stackCalc.push(chPop);
sText.push_back(chPop);
}

// 表达式还原计算
QString sNewExpr;
double dResultValue = sInputExpr.toDouble();
{
QString sOper;

// 计算逆波兰表达式：重新生成表达式
QStack<QString> stackTemp;
QStack<double> stackTempValue;
while (!stackCalc.empty())
{
QString sPop = stackCalc.pop();
if (sPop.length() == 0)
continue;

QChar ch = sPop.at(0);
if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{
if (stackTemp.size() >= 2)
{
sOper = sPop;
QString s1 = stackTemp.pop();
QString s2 = stackTemp.pop();
if ((sOper == "*" || sOper == "/") && (s2.contains('+') || s2.contains('-')))
{
s2 = "(" + s2 + ")";
}
sNewExpr = QString("%1 %2 %3").arg(s2).arg(sOper).arg(s1);
stackTemp.push(sNewExpr);

double d1 = stackTempValue.pop();
double d2 = stackTempValue.pop();
switch (ch.cell())
{
case '+':dResultValue = d2 + d1; break;
case '-':dResultValue = d2 - d1; break;
case '*':dResultValue = d2 * d1; break;
case '/':dResultValue = d2 / d1; break;
}
stackTempValue.push(dResultValue);
}
}
else
{
stackTemp.push(sPop);
stackTempValue.push(sPop.toDouble());
}
}
}
return QString("%1").arg(dResultValue);
}

核对1：(3.3949)*2+(3.3949)*3+(3.3949)*4 = 30.5541

核对2：(0.0242*0.3)*2 + (1.3411*0.3)*3 + (1.7969*0.3)*4 = 3.37779

核对3：2-1+3 = 4

 (Owed by: 春夜喜雨 http://blog.csdn.net/chunyexiyu)