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)) -> 6Stack
题目是用 stack 维护一个公式的进出,判断方法还可以,开始忘记数可能为负,后面改进了。
#include <stack> #include <iostream> #include <string> #include <vector> using namespace std; class Solution { public: int evalRPN(vector<string> &tokens) { int n = tokens.size(); stack<int > tmp; for(int i=0;i<n;i++){ if(tokens[i][0]>='0'&&tokens[i][0]<='9'){ tmp.push( helpFun(tokens[i]) ); continue; } if(tokens[i][0]=='-'&&tokens[i][1]!='