【练习3.21】
编写仅用一个数组而实现两个栈的例程。除非数组的每一个单元都被使用，否则栈例程不能有溢出声明。
Answer:
很简单，一个栈从数组头起，一个栈从数组尾起，分别保留左右栈头索引。
如left=5则表示array[0]~array[4]为左栈元素，right=7则表示array[8]~array[size-1]为右栈元素。
当左右索引交叉时(left=right+1)，0~left-1为左栈，left~size-1为右栈，刚好用完每一个单元。
测试代码：
1 #include <iostream> 2 #include "stack.h" 3 using namespace std; 4 using namespace stack; 5 template class Stack<int>; 6 int main(void) 7 { 8 Simu_Double_Stack<int> test(12); 9 //测试插入 10 test.leftpush(2); 11 test.leftpush(3); 12 test.leftpush(5); 13 test.leftpush(7); 14 test.leftpush(13); 15 test.rightpush(97); 16 test.rightpush(89); 17 test.rightpush(83); 18 test.rightpush(79); 19 test.rightpush(73); 20 test.rightpush(71); 21 //测试打印 22 test.leftprint(); 23 test.rightprint(); 24 cout << endl; 25 //测试拷贝 26 Simu_Double_Stack<int> test2; 27 test2 = test; 28 test2.leftprint(); 29 test2.rightprint(); 30 cout << endl; 31 //证明拷贝为深拷贝 32 test.leftpush(11); 33 test2.leftprint(); 34 cout << endl; 35 test.leftprint(); 36 cout << endl; 37 //测试栈满报错 38 test.leftpush(10); 39 test.rightpush(82); 40 //测试出栈 41 test.leftpop(); 42 test.leftpop(); 43 test.rightpop(); 44 test.rightpop(); 45 test.leftprint(); 46 test.rightprint(); 47 //测试栈元素清空 48 test.leftclear(); 49 test.rightclear(); 50 test.leftprint(); 51 test.rightprint(); 52 53 54 system("pause"); 55 }
实现代码：
1 //练习3.21新增，单数组模拟双栈 2 template <typename T> class Simu_Double_Stack 3 { 4 public: 5 Simu_Double_Stack() :head(nullptr), left(0), right(0), size(0){} 6 Simu_Double_Stack(unsigned int _size) 7 { 8 head = new T[_size]; 9 size = _size; 10 left = 0; 11 right = _size - 1; 12 } 13 Simu_Double_Stack(const Simu_Double_Stack& another) 14 { 15 size = another.size; 16 head = new T[size]; 17 left = another.left; 18 right = another.right; 19 for (int i = 0; i < size; ++i) 20 head[i] = another.head[i]; 21 } 22 ~Simu_Double_Stack(){ destory(); } 23 Simu_Double_Stack& operator=(const Simu_Double_Stack& another) 24 { 25 if (&another != this) 26 { 27 destory(); 28 size = another.size; 29 left = another.left; 30 right = another.right; 31 head = new T[size]; 32 for (unsigned int i = 0; i < size; ++i) 33 head[i] = another.head[i]; 34 } 35 return *this; 36 } 37 public: 38 //入栈 39 bool leftpush(const T& item) 40 { 41 if (left <= right) 42 { 43 head[left++] = item; 44 return true; 45 } 46 else 47 { 48 cout << "Overflow" << endl; 49 return false; 50 } 51 } 52 bool rightpush(const T& item) 53 { 54 if (right >= left) 55 { 56 head[right--] = item; 57 return true; 58 } 59 else 60 { 61 cout << "Overflow" << endl; 62 return false; 63 } 64 65 } 66 //出栈 67 bool leftpop() 68 { 69 if (left > 0) 70 { 71 --left; 72 return true; 73 } 74 else 75 { 76 cout << "Stack empty" << endl; 77 return false; 78 } 79 } 80 bool rightpop() 81 { 82 if (right < size - 1) 83 { 84 ++right; 85 return true; 86 } 87 else 88 { 89 cout << "Stack empty" << endl; 90 return false; 91 } 92 } 93 //获取长度信息 94 unsigned int leftsize()const{ return left; } 95 unsigned int rightsize()const{ return size - right - 1; } 96 unsigned int getsize()const{ return size; } 97 unsigned int getused()const{ return left + size - right - 1; } 98 //打印 99 void leftprint() const 100 { 101 for (unsigned int i = left - 1; i != -1; --i) 102 cout << " " << head[i] << flush; 103 } 104 void rightprint() const 105 { 106 for (unsigned int i = right + 1; i != size; ++i) 107 cout << " " << head[i] << flush; 108 } 109 //清空 110 void leftclear(){ left = 0; } 111 void rightclear(){ right = size - 1; } 112 private: 113 //释放内存 114 void destory() 115 { 116 left = right = size = 0; 117 delete[] head; 118 head = nullptr; 119 } 120 T* head = nullptr; 121 unsigned int left; 122 unsigned int right; 123 unsigned int size; 124 };