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
class Solution{
public:
int evalRPN(vector<string> &tokens) {
stack<int>ss;
string op="+-*/";
int isop;
for(int i=0;icout<int result;
if(isop==-1)
ss.push(atoi(tokens[i].c_str()));
else{
string temp_op=tokens[i];
int number_right=ss.top();
ss.pop();
int number_left=ss.top();
ss.pop();
switch(isop){
case 0:
result=number_left+number_right;
break;
case 1:
result=number_left-number_right;
break;
case 2:
result=number_left*number_right;
break;
case 3:
result=number_left/number_right;
break;
default:
result=-1;
break;
}
ss.push(result);
}
}
int final_result=ss.top();
return final_result;
}
};