LeetCode -- Evaluate Reverse Polish Notation

public class Solution {
    public int EvalRPN(string[] tokens) 
    {
        var stNo = new Stack<int>();
    	var stOp = new Stack<char>();
    	
    	for(var i = 0;i < tokens.Length; i++){
    		if(IsOp(tokens[i])){
    			if(stNo.Count == 0){
    				stOp.Push(tokens[i][0]);
    			}
    			else{
    				var n1 = stNo.Pop();
    				var n2 = stNo.Pop();
    				stNo.Push(Calc(n1, n2, tokens[i][0]));
    			}
    		}
    		else{
    			stNo.Push(int.Parse(tokens[i]));
    		}
    	}
	


    	while(stOp.Count > 0){
    		var op = stOp.Pop();
    		var n1 = stNo.Pop();
    		var n2 = stNo.Pop();
    		stNo.Push(Calc(n1, n2, op));
    	}
    	
    	return stNo.Pop();
    }


private int Calc(int n1 , int n2, char op)
{
	switch(op)
	{
		case ‘+‘:
			return n2 + n1;
		case ‘-‘:
			return n2 - n1;
		case ‘*‘:
			return n2 * n1;
		case ‘/‘:
			return n2 / n1;
		default:
			throw new NotSupportedException();
	}
}


private bool IsOp(string str)
{
	if(str == "+" || str == "-" || str == "*" || str == "/")
	{
		return true;
	}
	
	return false;
}
}

LeetCode -- Evaluate Reverse Polish Notation

原文：http://blog.csdn.net/lan_liang/article/details/49188215