LeetCode第一题:Evaluate Reverse Polish Notation
2014-06-11 22:10
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时间:2014.06.11
地点:基地
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Valid operators are
Each operand may be an integer or another expression.
Some examples:
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地点:基地
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一、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
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二、逆波兰求值问题,直接上源码
注意除法不满足交换律#include<vector> #include<stack> #include<string> #include<cctype> #include<iostream> using namespace std; class Solution { public: int evalRPN(vector<string> &tokens) { stack<int> my_stack_int; int lf = 0, rh = 0; for (auto& str : tokens) { if (isdigit(str[0])) my_stack_int.push(stoi(str)); else { rh = my_stack_int.top(); my_stack_int.pop(); lf = my_stack_int.top(); my_stack_int.pop(); switch (str[0]){ case '+': lf += rh;break; case '-': lf -= rh;break; case '/': lf /= rh;break; case '*': lf *= rh;break; default: break; } my_stack_int.push(lf); } } return my_stack_int.top(); } }; int main() { vector<string> str_vec{ "4", "13", "5", "/", "+" }; Solution sl; int a = sl.evalRPN(str_vec); cout << a << endl; }
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