LeetCode Evaluate Reverse Polish Notation

链接: https://oj.leetcode.com/problems/evaluate-reverse-polish-notation/

后缀表达式求值

class Solution
{
	public:
		int evalRPN(vector<string> &tokens)
		{
			stack<int> stk;
			int ans=0;
			for(int i=0;i<tokens.size();i++)
			{
				string tem=tokens[i];
				if((tem[0]>='0'&&tem[0]<='9')||(tem[1]>='0'&&tem[1]<='9'))			//为数字
				{
					stk.push(atoi(tem.c_str()));
				}
				else				//为字符
				{
						int a=stk.top();
						stk.pop();
						int b=stk.top();
						stk.pop();
						if(tem=="+")
						    ans=b+a;
						if(tem=="-")
						    ans=b-a;
						if(tem=="*")
						    ans=b*a;
						if(tem=="/")
						    ans=b/a;
						stk.push(ans);
				}
			}
			return stk.top();
		}
};