数据结构与算法 - 栈的实现

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栈结构

栈是一种特殊的线性结构(先进后出)

顺序栈实现

顺序栈的数据结构
#define OK 1
#define ERROR 0
#define MAXSIZE 20 /* 存储空间初始分配量 */

typedef int Status;
typedef int SElemType; /* SElemType类型根据实际情况而定,这里假设为int */

/* 顺序栈结构 */
typedef struct
{
    SElemType data[MAXSIZE];
    int top; /* 用于栈顶指针  -1代表空栈*/
}SqStack;
顺序栈操作
// 构建一个空栈S
Status InitStack(SqStack *S){
   
    S->top = -1;
    return OK;
}


// 将栈置空
Status ClearStack(SqStack *S){
    
    //疑问: 将栈置空,需要将顺序栈的元素都清空吗?
    //不需要,只需要修改top标签就可以了.
    S->top = -1;
    return OK;
}

// 判断顺序栈是否为空;
Status StackEmpty(SqStack S){
    if (S.top == -1)
        return TRUE;
    else
        return FALSE;
}

// 返回栈的长度
int StackLength(SqStack S){
    return S.top + 1;
}

// 获取栈顶
Status GetTop(SqStack S,SElemType *e){
    if (S.top == -1)
        return ERROR;
    else
        *e = S.data[S.top];
   
    return OK;
    
}

// 插入元素e为新栈顶元素
Status PushData(SqStack *S, SElemType e){
    
    //栈已满
    if (S->top == MAXSIZE -1) {
        return ERROR;
    }
    
    //栈顶指针+1;
    S->top ++;
    //将新插入的元素赋值给栈顶空间
    S->data[S->top] = e;
    
    return OK;
}

// 删除S栈顶元素,并且用e带回
Status Pop(SqStack *S,SElemType *e){
   
    //空栈,则返回error;
    if (S->top == -1) {
        return ERROR;
    }
    
    //将要删除的栈顶元素赋值给e
    *e = S->data[S->top];
    //栈顶指针--;
    S->top--;
    
    return OK;
}

// 从栈底到栈顶依次对栈中的每个元素打印
Status StackTraverse(SqStack S){
    int i = 0;
    printf("此栈中所有元素");
    while (i<=S.top) {
        printf("%d ",S.data[i++]);
    }
    printf("\n");
    return OK;
}

// main函数
int main(int argc, const char * argv[]) {
    // insert code here...
    printf("顺序栈的表示与实现!\n");
    
    SqStack S;
    int e;
    
    if (InitStack(&S) == OK) {
        for (int j = 1 ; j < 10; j++) {
            PushData(&S, j);
        }
    }
    
    printf("顺序栈中元素为:\n");
    StackTraverse(S);
    
    Pop(&S, &e);
    printf("弹出栈顶元素为: %d\n",e);
    StackTraverse(S);
    printf("是否为空栈:%d\n",StackEmpty(S));
    GetTop(S, &e);
    printf("栈顶元素:%d \n栈长度:%d\n",e,StackLength(S));
    ClearStack(&S);
    printf("是否已经清空栈 %d, 栈长度为:%d\n",StackEmpty(S),StackLength(S));
    

    return 0;
}

链式栈实现

链式栈数据结构
//栈元素
typedef struct StackNode
{
    SElemType data;
    struct StackNode *next;
}StackNode,*LinkStackPtr;

//栈结构
typedef struct
{
    LinkStackPtr top;
    int count;
}LinkStack;
链式栈操作
/* 构造一个空栈S */
Status InitStack(LinkStack *S)
{
    S->top=NULL;
    S->count=0;
    return OK;
}


/* 把链栈S置为空栈 链式栈需手动释放每个节点*/
Status ClearStack(LinkStack *S){
    LinkStackPtr p,q;
    p = S->top;
    while (p) {
        q = p;
        p = p->next;
        free(q);
    }
    S->count = 0;
    return OK;
}

/* 若栈S为空栈,则返回TRUE, 否则返回FALSE*/
Status StackEmpty(LinkStack S){
    if (S.count == 0)
        return TRUE;
    else
        return FALSE;
}

/* 返回S的元素个数,即栈的长度*/
int StackLength(LinkStack S){
    return S.count;
}

/* 若链栈S不为空,则用e返回栈顶元素,并返回OK ,否则返回ERROR*/
Status GetTop(LinkStack S,SElemType *e){
    if(S.top == NULL)
        return ERROR;
    else
        *e = S.top->data;
    return OK;
}

/* 插入元素e到链栈S (成为栈顶新元素)*/
Status Push(LinkStack *S, SElemType e){
    
    //创建新结点temp
    LinkStackPtr temp = (LinkStackPtr)malloc(sizeof(StackNode));
    //赋值
    temp->data = e;
    //把当前的栈顶元素赋值给新结点的直接后继
    temp->next = S->top;
    //将新结点temp 赋值给栈顶指针
    S->top = temp;
    S->count++;
    return OK;
}

/* 若栈不为空,则删除S的栈顶元素,用e返回其值. 并返回OK,否则返回ERROR*/
Status Pop(LinkStack *S,SElemType *e){
    LinkStackPtr p;
    if (StackEmpty(*S)) {
        return ERROR;
    }
    
    //将栈顶元素赋值给*e
    *e = S->top->data;
    //将栈顶结点赋值给p,参考图例①
    p = S->top;
    //使得栈顶指针下移一位, 指向后一结点. 参考图例②
    S->top= S->top->next;
    //释放p
    free(p);
    //个数--
    S->count--;
    
    return OK;
}

/* 遍历链栈*/
Status StackTraverse(LinkStack S){
    LinkStackPtr p;
    p = S.top;
    while (p) {
        printf("%d ",p->data);
        p = p->next;
    }
    printf("\n");
    return OK;
}


int main(int argc, const char * argv[]) {
    // insert code here...
    printf("链栈定义与实现\n");
    
    int j;
    LinkStack s;
    int e;
    if(InitStack(&s)==OK)
        for(j=1;j<=10;j++)
            Push(&s,j);
    printf("栈中元素依次为:");
    StackTraverse(s);
    Pop(&s,&e);
    printf("弹出的栈顶元素 e=%d\n",e);
    StackTraverse(s);
    printf("栈空否:%d(1:空 0:否)\n",StackEmpty(s));
    GetTop(s,&e);
    printf("栈顶元素 e=%d 栈的长度为%d\n",e,StackLength(s));
    ClearStack(&s);
    printf("清空栈后,栈空否:%d(1:空 0:否)\n",StackEmpty(s));
    
    return 0;
}