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Evaluate Reverse Polish Notation

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Description

https://leetcode.com/problems/evaluate-reverse-polish-notation/description/

Solution

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class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        if (tokens.size() == 0) return 0;
        
        stack<int> numberStack;
        int index = 0;
        
        while(index < tokens.size()) {
            int left, right;
            string token = tokens[index];
            index += 1;
            
            if (token == "+"){
                left = numberStack.top();
                numberStack.pop();
                right = numberStack.top();
                numberStack.pop();
                numberStack.push(left + right);
                continue;
            }
                    
            if (token == "-" and token.length() == 1) {
                left = numberStack.top();
                numberStack.pop();
                right = numberStack.top();
                numberStack.pop();
                numberStack.push(right - left);
                continue;
            }
                    
            if(token == "/") {
                left = numberStack.top();
                numberStack.pop();
                right = numberStack.top();
                numberStack.pop();
                numberStack.push(right / left);
                continue;
            }
            
            if(token == "*") {
                left = numberStack.top();
                numberStack.pop();
                right = numberStack.top();
                numberStack.pop();
                numberStack.push(right * left);
                continue;
            }
            
            int number = stoi(token);
            numberStack.push(number);
        }
        return numberStack.top();
    }
};