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Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are +, -, *, /. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6
class Solution { public: int evalRPN(vector<string> &tokens) { int sum; string operators="+-*/"; stack<int>sta; for(int i=0;i<tokens.size();i++){ if(operators.find(tokens[i])==string::npos){ sta.push(atoi(tokens[i].c_str())); } else{ int a=sta.top(); sta.pop(); int b=sta.top(); sta.pop(); if(tokens[i]=="+"){ sta.push(a+b); } if(tokens[i]=="-"){ sta.push(b-a); } if(tokens[i]=="*"){ sta.push(a*b); } if(tokens[i]=="/"){ sta.push(b/a); } } } sum=sta.top(); return sum; } };
Evaluate Reverse Polish Notation
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原文地址：http://www.cnblogs.com/mrpod2g/p/4265573.html
