【LeetCode】Evaluate Reverse Polish Notation

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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class Solution {public:    bool isoperator(string op)    {    if(op == "+" || op == "-" || op == "*" || op == "/")    return true;   else return false;    }    int compute(int op1, int op2, string op)        {    if(op == "+"){    return op1+op2;    }    else if(op == "-"){    return op1-op2;    }    else if(op == "*"){    return op1*op2;    }    else return op1/op2;    }    int evalRPN(vector<string> &tokens) {        if(tokens.size() == 1){return atoi(tokens[0].c_str());    }        stack<string> buf;    for(int i = 0; i < tokens.size(); i++)    {    if(isoperator(tokens[i])){string op1 = buf.top();int ope1 = atoi(op1.c_str());buf.pop();string op2 = buf.top();int ope2 = atoi(op2.c_str());buf.pop();int tmp = compute(ope2,ope1,tokens[i]);if(i == tokens.size()-1){return tmp;}else {char buffer[64];//itoa(tmp,buffer,10);sprintf(buffer,"%d",tmp);string res(buffer);buf.push(res);}}else buf.push(tokens[i]);    }    }};