栈、队列&leetcode225&155&232

• c++中栈的简单应用
• 定义
  #include < stack >
  template < class T, class Container = deque< T > > class stack;
  stack< int > sta; //栈中均为int；
  用数组实现一个栈～～

class stack     {     private:         int arr[MAX];       int top;   public:         stack()       {             inItStack();       }  //初始化栈                                                                         void inItStack()       {           top=-1;       }       //入栈                                                                         void push(int a)       {             top++;          if(top < MAX)  {                 arr[top]=a;           }   else   {                 cout<<"STACK FULL!!"<<top;             }         }         //出栈                                                                          void pop()      {              if(empty())   {                 cout<<"STACK IS EMPTY ";          }         else {                 int data=arr[top];               arr[top]=NULL;               top--;          }         }    int top(){        if(empty()){            cout<<"stack is empty";        }        else            return arr[top];    }         //是否为空                                                                        bool empty()      {          if(top == -1)             return true;          else             return false;      }  };     

• 应用
  sta.empty()　　　　　　如果栈为空返回true，否则返回false；
  sta.size()　　　　　　　 返回int，栈内元素的大小；
  sta.pop()　　　　　　　返回void；删除栈顶元素;
  sta.push()　　　　　　 返回void；向栈内压入一个成员；
  sta.top()　　　　　　 返回int；返回栈顶元素；
• c++中队列的简单应用
• 定义： #include< queue >
  queue< int > que;

用链表实现队列～～

#include<iostream>using namespace std;template <typename T>struct Node{    Node(T &d){        data=d;        next=NULL;    }    T data;    Node *next;};template <typename T>class LinkQueue{    private:        int length;        Node<T> *front;        Node<T> *rear;    public:        LinkQueue(T &n){            Node <T> *p=new Node<T>(n);            length=0;            front=rear=p;        }        bool Queuelength()        {            cout<<"当前队列长度："<<length<<endl;            return true;        }        bool IsEmpty(){            return length==0;        }        void EnQueue(T n)        {            Node<T> *p=new Node<T>(n);            rear->next=p;            rear=p;            length++;        }        bool DelQueue(){            if(front==rear)              return false;            Node<T> *p=front->next;            front->next=p->next;            if(front->next==NULL)                rear=front;            delete p;            length--;            return true;        }        void Tranverse()        {            Node<T> *p=front->next;            cout<<"遍历队列："<<endl;            while(p!=NULL)            {                cout<<p->data<<" ";                p=p->next;            }            cout<<endl;        }};

• 应用
  back()返回最后一个元素，顶部
  empty()如果队列空则返回真
  front()返回第一个元素，底部
  pop()删除第一个元素，底部
  push()在末尾加入一个元素，顶部
  size()返回队列中元素的个数

1、Min Stack
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

push(x) – Push element x onto stack.
pop() – Removes the element on top of the stack.
top() – Get the top element.
getMin() – Retrieve the minimum element in the stack.
Example:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); –> Returns -3.
minStack.pop();
minStack.top(); –> Returns 0.
minStack.getMin(); –> Returns -2.

class MinStack {private:    stack<int> a;    stack<int> a_min;public:    void push(int x) {        a.push(x);        if(a_min.empty()||((!a_min.empty())&&x<=a_min.top())){            a_min.push(x);        }    }    void pop() {        if(!a.empty()){            if(a.top()==a_min.top()){                a_min.pop();            }            a.pop();        }    }    int top() {        if(!a.empty())            return a.top();    }    int getMin() {        if(!a_min.empty())            return a_min.top();    }};/** * Your MinStack object will be instantiated and called as such: * MinStack obj = new MinStack(); * obj.push(x); * obj.pop(); * int param_3 = obj.top(); * int param_4 = obj.getMin(); */

2、Implement Stack using Queues
Implement the following operations of a stack using queues.

push(x) – Push element x onto stack.
pop() – Removes the element on top of the stack.
top() – Get the top element.
empty() – Return whether the stack is empty.
Notes:
You must use only standard operations of a queue – which means only push to back, peek/pop from front, size, and is empty operations are valid.
Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

class Stack {private:    queue<int> que;public:    // Push element x onto stack.    void push(int x) {        que.push(x);        for(int i=0;i<que.size()-1;i++){            que.push(que.front());            que.pop();        }    }    // Removes the element on top of the stack.    void pop() {        que.pop();    }    // Get the top element.    int top() {        return que.front();    }    // Return whether the stack is empty.    bool empty() {        return que.empty();    }};

3、Implement Queue using Stacks
Implement the following operations of a queue using stacks.

push(x) – Push element x to the back of queue.
pop() – Removes the element from in front of queue.
peek() – Get the front element.
empty() – Return whether the queue is empty.
Notes:
You must use only standard operations of a stack – which means only push to top, peek/pop from top, size, and is empty operations are valid.
Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

class Queue {    stack<int> in,out;public:    // Push element x to the back of queue.    void push(int x) {        in.push(x);    }    // Removes the element from in front of queue.    void pop(void) {        peek();        out.pop();    }    // Get the front element.    int peek(void) {        if(out.empty()){            while(!in.empty()){                out.push(in.top());                in.pop();            }        }        return out.top();    }    // Return whether the queue is empty.    bool empty(void) {        return in.empty()&&out.empty();    }};