双栈：数组实现

双栈：数组实现

结构描述：

#include <iostream>
#include <cstdlib>
#define MAX 100
using namespace std;

typedef int DataType;
class DoubleStack {
public:
    DataType *A;
    //两个栈的栈顶
    int TP;
    int TB;

    //建立一个空栈
    void Init();
    //判空、判满
    bool IsEmpty();
    bool IsFull();
    //入栈，根据Top的值入栈
    void Push(DataType X, int Top);
    //出栈，根据Top的值出栈
    void Pop(int Top);
    //摧毁栈
    void MakeEmpty();
    //获取栈顶元素，根据栈顶的值
    DataType GetTopValue(int Top);

    //获取两个栈顶的指针
    int GetTP();
    int GetTB();
};

初始化

栈顶指针分别置为 -1 和 MAX 即可；

为 A 分配空间

void DoubleStack::Init() {
    A = (DataType *)malloc(sizeof (DataType) * MAX);
    TP = -1;
    TB = MAX;
}

判空、判满

栈空时即两个栈顶都是初始位置

栈满时，TP + 1 == TB

bool DoubleStack::IsFull() {
    return TP + 1 == TB;
}

bool DoubleStack::IsEmpty() {
    return TP == -1 && TB == MAX;
}

入栈

• 栈满：报错
• 非满：
  • 根据传入的参数，选择对哪个栈进行操作；
  • Top == TP 则 A[++TP] = X;
  • Top == TB 则 A[--TB] = X;

void DoubleStack::Push(DataType X, int Top) {
    //栈非空
    if (IsFull()) {
        cout << "Stack Is Full!" << endl;
        exit(-1);
    }

    if (Top == TP) {
        A[++TP] = X;
    }

    else if (Top == TB) {
        A[--TB] = X;
    }
    else {
        cout << "This is not the top of the stack!" << endl;
        exit(-1);
    }
}

出栈

• 栈空：报错
• 非空：
  • 根据栈顶的值来进行操作：
    • if (Top == TP) TP--;
    • if (Top == TB) TB++;
    • else Err;

void DoubleStack::Pop(int Top) {
    if (IsEmpty()) {
        cout << "Stack is Empty!" << endl;
        exit(-1);
    }

    if (Top == TP) {
        TP--;
    }
    else if (Top == TB) {
        TB++;
    }
    else {
        cout << "This is not the top of stack!" << endl;
        exit(-1);
    }
}

获取栈顶元素

• 栈空：报错
• 非空：根据传入的栈顶信息，直接返回

DataType DoubleStack::GetTopValue(int Top) {
    if (IsEmpty()) {
        cout << "Stack is empty!\n";
        exit(-1);
    }
    else {
        return A[Top];
    }
}

摧毁

• 栈空：报错
• 非空：一直出栈，直至栈空

void DoubleStack::MakeEmpty() {
    if (IsEmpty()) {
        cout << "Stack is empty!\n";
        exit(-1);
    }

    while (TP != -1) {
        Pop(TP);
    }

    while (TB != MAX) {
        Pop(TB);
    }
}

获取栈顶指针

• 栈空：报错
• 非空：返回

int DoubleStack::GetTP() {
    if (IsEmpty()) {
        cout << "Stack is empty!\n";
        exit(-1);
    }
    return TP;
}
int DoubleStack::GetTB() {
    if (IsEmpty()) {
        cout << "Stack is empty!\n";
        exit(-1);
    }   
    return TB;
}

错误记录

把TP自增，却用Top为下标给其赋值，怪不得会出错

void DoubleStack::Push(DataType X, int Top) {
    if (Top == TP) {
        TP++;
    }

    else if (Top == TB) {
        TB--;
    }
    else {
        cout << "This is not the top of the stack!" << endl;
        exit(-1);
    }

    A[Top] = X;
}