标签：style blog class code c java
题目：
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
解题思路：
遇到数字则将其压入栈中，遇到运算符就弹出栈顶的两个元素做相应的运算，然后将运算结果压入栈中。
最后的结果保存在栈顶。
代码：
class Solution { public: int evalRPN(vector<string> &tokens) { stack<int> st; int operand_a = 0, operand_b = 0, tmp; stringstream ss; vector<string>::iterator it; for(it = tokens.begin(); it != tokens.end(); it++){ ss.clear(); if ((*it) == "+" ){ operand_b = st.top(); st.pop(); operand_a = st.top(); st.pop(); st.push(operand_a + operand_b); } else if ((*it) == "-" ){ operand_b = st.top(); st.pop(); operand_a = st.top(); st.pop(); st.push(operand_a - operand_b); } else if ((*it) == "*" ){ operand_b = st.top(); st.pop(); operand_a = st.top(); st.pop(); st.push(operand_a * operand_b); } else if ((*it) == "/" ){ operand_b = st.top(); st.pop(); operand_a = st.top(); st.pop(); st.push(operand_a / operand_b); } else{ ss.str(*it); ss >> tmp; st.push(tmp); } } return st.top(); } };
LeetCode OJ - Evaluate Reverse Polish Notation,布布扣,bubuko.com
LeetCode OJ - Evaluate Reverse Polish Notation
标签：style blog class code c java
原文地址：http://www.cnblogs.com/dongguangqing/p/3726272.html
