使用两个栈实现一个队列+使用两个队列实现一个栈

1. 使用两个栈实现一个队列+使用两个队列实现一个栈

1. 两个栈实现一个队列

#include<iostream>


#include<stack>

using namespace std;
template<class T>
class StackQueue
{
public:
    void Push(T data)
    {
        Spush.push(data);
    }
    void Pop()
    {
        if (Spop.empty())
        {
            while (!Spush.empty())
            {
                Spop.push(Spush.top());
                Spush.pop();
            }
        }
        Spop.pop();
    }
    T Front()
    {
        if (Spop.empty())
        {
            while (!Spush.empty())
            {
                Spop.push(Spush.top());
                Spush.pop();
            }
        }
        return Spop.top();
    }
    bool empty()
    {
        return Spop.empty() && Spush.empty();
    }
private:
    stack<T> Spop;
    stack<T> Spush;

};
int main()
{
    StackQueue<int> q;
    q.Push(3);
    q.Push(4);
    q.Push(5);
    q.Push(6);
    q.Push(7);
    q.Push(8);
    q.Push(9);
    q.Push(10);
    while (!q.empty())
    {
        cout << q.Front() << " ";
        q.Pop();
    }

    system("pause");
}

1. 两个队列实现一个栈

#include<iostream>


#include<queue>

using namespace std;
template<class T>
class QueueStack
{
public:
    void Pop()
    {
        while (PushQ.size() > 1)
        {
            PopQ.push(PushQ.front());
            PushQ.pop();
        }
        PushQ.pop();
        while (!PopQ.empty())
        {
            PushQ.push(PopQ.front());
            PopQ.pop();
        }
    }
    void Push(T data)
    {
        PushQ.push(data);
    }
    T Top()
    {
        while (PushQ.size() > 1)
        {
            PopQ.push(PushQ.front());
            PushQ.pop();
        }
        T top=PushQ.front();
        PopQ.push(PushQ.front());
        PushQ.pop();
        while (!PopQ.empty())
        {
            PushQ.push(PopQ.front());
            PopQ.pop();
        }
        return top;
    }
    bool Empty()
    {
        return  PushQ.empty()&& PopQ.empty();
    }
private:
    queue<T> PopQ;
    queue<T> PushQ;
};
int main()
{
    QueueStack<int> s;
    s.Push(5);
    s.Push(6);
    s.Push(7);
    while (!s.Empty())
    {
        cout << s.Top() << " ";
        s.Pop();
    }
    system("pause");
};

2. 将字符串的空格替换成%20

```
#include<iostream>
using namespace std;
int getBlankCount(const char *arr, int len)
{
    int count = 0;
    for (int i = 0; i < len; i++)
    {
        if (arr[i] == ' ')
            ++count;
    }
    return count;
}
void addTo20(char *arr, int len)
{
    if (arr == nullptr || len <= 0)
        return;
    int tail = len;
    int count = getBlankCount(arr,len);
    int end = 2 * count + tail;
    while (tail < end)
    {
        if (arr[tail] == ' ')
        {
            arr[end--] = '%';
            arr[end--] = '0';
            arr[end--] = '2';
        }
        else
            arr[end--] = arr[tail];
        --tail;
    }
}
int main()
{
    char arr[100] = " are you ok ";
    int len = strlen(arr);
    addTo20(arr, len);
    cout << arr << endl;
    system("pause");
}
```