代码随想录训练营第十天

Leetcode 232.用栈实现队列

题目链接：用栈实现队列
Solution：

• 栈 队列

class MyQueue {
private:
    stack<int> inStack, outStack;

    void in2out() {
        while (!inStack.empty()) {
            outStack.push(inStack.top());
            inStack.pop();
        }
    }

public:
    MyQueue() {}

    void push(int x) {
        inStack.push(x);
    }

    int pop() {
        if (outStack.empty()) {
            in2out();
        }
        int x = outStack.top();
        outStack.pop();
        return x;
    }

    int peek() {
        if (outStack.empty()) {
            in2out();
        }
        return outStack.top();
    }

    bool empty() {
        return inStack.empty() && outStack.empty();
    }
};

Leetcode 225. 用队列实现栈

题目链接：用队列实现栈
Solution：

• 栈 队列

class MyStack {
public:
    queue<int> queue1;
    queue<int> queue2;

    /** Initialize your data structure here. */
    MyStack() {

    }

    /** Push element x onto stack. */
    void push(int x) {
        queue2.push(x);
        while (!queue1.empty()) {
            queue2.push(queue1.front());
            queue1.pop();
        }
        swap(queue1, queue2);
    }
    
    /** Removes the element on top of the stack and returns that element. */
    int pop() {
        int r = queue1.front();
        queue1.pop();
        return r;
    }
    
    /** Get the top element. */
    int top() {
        int r = queue1.front();
        return r;
    }
    
    /** Returns whether the stack is empty. */
    bool empty() {
        return queue1.empty();
    }
};