栈和队列相关面试题（3）

5、一个数组实现两个栈
思路：双向增长法
      两个栈的栈底分别指向数组的两端，栈顶不断向另一个栈的栈底靠近。
过程：
      1、假设以数组首端为栈底的栈叫Stack1，以数组尾端为栈底的栈Stack2，那么当Stack1的栈顶指针大于Stack2的栈顶指针时，需扩容
      2、在实现Push与Pop操作是需要多传一个参数flag以确定是对哪一个栈进行操作

思路2：交替索引法/交叉索引-->缺点：空间的浪费，若是一个栈满，另一个栈还没存东西，此时本来还可以向数组里面存东西，不过要是向
                                   已经栈满的栈插入元素，那么就会因空间不够而开辟空间，这就是空间的浪费
                             优点：不仅可以用一个数组实现两个栈，还可以实现多个栈

 

 

StackAndQueue.h

<strong><span style="font-size:18px;">#pragma once#include <iostream>#include <assert.h>using namespace std;template<class T>class ArrayForTwoStack{public:ArrayForTwoStack():_array(NULL),_capacity(0),top1(-2),top2(-1){}ArrayForTwoStack(const ArrayForTwoStack& stack){_array = new T[stack._capacity];_capacity = stack._capacity;top1 = stack.top1;top2 = stack.top2;int count = top1 > top2 ? top1 : top2;for (size_t index = 0;index < count; ++index){_array[index] = stack._array[index];}}~ArrayForTwoStack(){if (_array){delete[] _array;_array = NULL;}}void Push(size_t flag,const T& data){CheckCapacity();//用flag来判断是哪一个栈中存放数据if (flag == 1)//flag为1时，下标为偶数存放栈1的数据{top1 += 2;_array[top1] = data;} else//当flag不为1时，下标为奇数存放栈2的数据{top2 += 2;_array[top2] = data;}}void Pop(size_t flag){if (flag == 1){assert(top1 != -2);top1 -= 2;} else{assert(top2 != -1);top2 -= 2;}}T& Top(size_t flag){if (flag == 1){assert(top1 != -2);return _array[top1];} else{assert(top2 != -1);return _array[top2];}}bool Empty(size_t flag){if (flag == 1){if (top1 == -2){return true;} else{return false;}} else{if (top2 == -1){return true;} else{return false;}}}size_t Size(size_t flag){if (flag == 1){assert(top1 != -2);return top1/2 + 1;} else{assert(top2 != -1);return (top2 + 1)/2;}}protected:void CheckCapacity(){if (((top1 + 2) >= _capacity) || ((top2 + 2) >= _capacity)){_capacity = _capacity * 2 + 3;T* tmp = new T[_capacity];int count = top1 > top2 ? top1 : top2;for (int index = 0;index <= count; ++index){tmp[index] = _array[index];}delete[] _array;_array = tmp;}}private:T* _array;size_t _capacity;int top1;//stack1的栈顶下标int top2;//stack2的栈顶下标};</span></strong>

 

test.cpp

<strong><span style="font-size:18px;">#define _CRT_SECURE_NO_WARNINGS 1#include "StackAndQueue.h"void Test5(){//一个数组实现两个栈ArrayForTwoStack<int> stack;stack.Push(1,1);stack.Push(1,2);stack.Push(1,3);stack.Push(1,4);stack.Push(1,5);cout<<stack.Top(1)<<endl;cout<<stack.Empty(1)<<endl;cout<<stack.Size(1)<<endl;stack.Pop(1);stack.Pop(1);cout<<stack.Top(1)<<endl;cout<<stack.Empty(1)<<endl;cout<<stack.Size(1)<<endl;stack.Push(2,6);stack.Push(2,7);stack.Push(2,8);stack.Push(2,9);stack.Push(2,10);cout<<stack.Top(2)<<endl;cout<<stack.Empty(2)<<endl;cout<<stack.Size(2)<<endl;stack.Pop(2);stack.Pop(2);cout<<stack.Top(2)<<endl;cout<<stack.Empty(2)<<endl;cout<<stack.Size(2)<<endl;}int main(){Test5();system("pause");return 0;}</span></strong>