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逆波兰表达式解数学运算（c#)
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逆波兰表达式解数学运算 感谢作者 http://blog.csdn.net/liuyuxusuixiang/article/details/25289715
public class TCalculator
{
Dictionary<char, int> priorities = null;
const string operators = "+-*/%^";
public TCalculator()
{
priorities = new Dictionary<char, int>();
priorities.Add('#', -);
priorities.Add('+', );
priorities.Add('-', );
priorities.Add('*', );
priorities.Add('/', );
priorities.Add('%', );
priorities.Add('^', );
} double Compute(double leftNum, double rightNum, char op)
{
switch (op)
{
case '+': return leftNum + rightNum;
case '-': return leftNum - rightNum;
case '*': return leftNum * rightNum;
case '/': return leftNum / rightNum;
case '%': return leftNum % rightNum;
case '^': return Math.Pow(leftNum, rightNum);
default: return ;
}
} bool IsOperator(char op)
{
return operators.IndexOf(op) >= ;
} bool IsLeftAssoc(char op)
{
return op == '+' || op == '-' || op == '*' || op == '/' || op == '%';
} Queue<object> PreOrderToPostOrder(string expression)
{
var result = new Queue<object>();
var operatorStack = new Stack<char>();
operatorStack.Push('#');
char top, cur, tempChar;
string tempNum;
if (expression[] == '-') expression = '' + expression; for (int i = , j; i < expression.Length; )
{
cur = expression[i++];
top = operatorStack.Peek(); if (cur == '(')
{
operatorStack.Push(cur);
}
else
{
if (IsOperator(cur))
{
while (IsOperator(top) && ((IsLeftAssoc(cur) && priorities[cur] <= priorities[top])) || (!IsLeftAssoc(cur) && priorities[cur] < priorities[top]))
{
result.Enqueue(operatorStack.Pop());
top = operatorStack.Peek();
}
operatorStack.Push(cur);
}
else if (cur == ')')
{
while (operatorStack.Count > && (tempChar = operatorStack.Pop()) != '(')
{
result.Enqueue(tempChar);
}
}
else
{
tempNum = "" + cur;
j = i;
while (j < expression.Length && (expression[j] == '.' || (expression[j] >= '' && expression[j] <= '')))
{
tempNum += expression[j++];
}
i = j;
result.Enqueue(tempNum);
}
}
}
while (operatorStack.Count > )
{
cur = operatorStack.Pop();
if (cur == '#') continue;
if (operatorStack.Count > )
{
top = operatorStack.Peek();
} result.Enqueue(cur);
} return result;
} public double Calucate(string expression)
{
try
{
var rpn = PreOrderToPostOrder(expression);
var operandStack = new Stack<double>();
double left, right;
object cur;
while (rpn.Count > )
{
cur = rpn.Dequeue();
if (cur is char)
{
right = operandStack.Pop();
left = operandStack.Pop();
operandStack.Push(Compute(left, right, (char)cur));
}
else
{
operandStack.Push(double.Parse(cur.ToString()));
}
}
return operandStack.Pop();
}
catch
{
throw new Exception("表达式格式不正确！");
}
}
class MainClass
{
public static void Main (string[] args)
{ Console.WriteLine((new TCalculator()).Calucate("1+2+3+4").ToString());
Console.WriteLine((new TCalculator()).Calucate("1+1%3+4").ToString());
Console.WriteLine((new TCalculator()).Calucate("1+1-3+4").ToString());
Console.WriteLine((new TCalculator()).Calucate("").ToString());
Console.WriteLine((new TCalculator()).Calucate("2-1+3").ToString());
Console.WriteLine((new TCalculator()).Calucate("2-(1+3)").ToString());
Console.WriteLine((new TCalculator()).Calucate("11-(15+30)").ToString());
Console.ReadKey();
}
}
