【C++】栈练习_c++ 栈编程题目

eg1

class Solution {
public:
    bool IsPopOrder(vector<int> pushV,vector<int> popV) {
        stack<int> st;
        int pushi = 0;
        int popi = 0;
        for(pushi = 0; pushi < pushV.size(); ++pushi)
        {
            //先入栈
            st.push(pushV[pushi]);
            //判断入栈的值是否和出栈的值相等。
            while(!st.empty() && st.top() == popV[popi])
            {
                st.pop();
                ++popi;
            }
        }
        
        return popi == popV.size();
    }
};
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eg2

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> st;

        for(int i = 0; i < tokens.size(); ++i)
        {
            if(tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" || tokens[i] == "/")
            {
                int right = st.top();
                st.pop();
                int left = st.top();
                st.pop();
                //将计算的结果入栈
                if(tokens[i] == "+")
                {
                    st.push(left + right);
                }
                else if(tokens[i] == "-")
                {
                    st.push(left - right);
                }
                else if(tokens[i] == "*")
                {
                    st.push(left * right);
                }
                else
                {
                    st.push(left / right);
                }
            }

            else 
            {
                st.push(stoi(tokens[i]));
            }
        }

        return st.top();

    }
};
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