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leetcode - [2]Evaluate Reverse Polish Notation
Evaluate Reverse Polish Notation
Total Accepted: 24595 Total Submissions: 123794My Submissions
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
思路：栈的简单应用
#include <iostream>#include <vector>#include <string>#include <stack>#include <cstdlib>using namespace std;class Solution {public: int evalRPN(vector<string> &tokens) { stack<int> s; string str; int a, b; for (int i = 0; i < tokens.size(); i++) { str = tokens[i]; if (str == "+" || str == "-" || str == "*" || a = s.top(); s.pop(); b = s.top(); s.pop(); switch(str[0]) { case ‘+‘: s.push(b+a); break; case ‘-‘: s.push(b-a); break; case ‘*‘: s.push(b*a); break; case ‘/‘: s.push(b/a); break; } } else { s.push(atoi(str.c_str())); } } a = s.top();s.pop(); return a; }};int main(int argc, char *argv[]) { Solution* solution = new Solution(); vector<string> tokens; tokens.push_back("2"); tokens.push_back("1"); tokens.push_back("+"); tokens.push_back("3"); tokens.push_back("*"); cout << solution->evalRPN(tokens) << endl; vector<string> tokens2; tokens2.push_back("4"); tokens2.push_back("13"); tokens2.push_back("5"); tokens2.push_back("/"); tokens2.push_back("+"); cout << solution->evalRPN(tokens2) << endl; return 0;}
leetcode - [2]Evaluate Reverse Polish Notation
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