标签：style blog http color io ar strong for sp
题目描述：
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
解题方案：
该题借助一个栈，遍历tokens时，如果当前不为"+","-","*","/"，则入栈，否则将栈顶的两个元素出栈后，运算后结果入栈。下面是该题代码：
1 class Solution { 2 public: 3 int evalRPN(vector<string> &tokens) { 4 stack<int> result; 5 int a, b; 6 for (vector<string>::iterator ix = tokens.begin(); ix != tokens.end(); ++ix) { 7 if (*ix == "+" || *ix == "-" || *ix == "*" || *ix == "/") { 8 a = result.top(); 9 result.pop(); 10 b = result.top(); 11 result.pop(); 12 if (*ix == "+") { 13 result.push(b + a); 14 } 15 if (*ix == "-") { 16 result.push(b - a); 17 } 18 if (*ix == "*") { 19 result.push(b * a); 20 } 21 if (*ix == "/") { 22 result.push(b / a); 23 } 24 } else { 25 result.push(atoi((*ix).c_str())); 26 } 27 } 28 return result.top(); 29 } 30 };
Evaluate Reverse Polish Notation
标签：style blog http color io ar strong for sp
原文地址：http://www.cnblogs.com/skycore/p/3997672.html
