python算法与数据结构-栈(43)

一、栈的介绍

  栈作为一种数据结构,是一种只能在一端进行插入和删除操作。它按照先进后出的原则存储数据,先进入的数据被压入栈底,最后的数据在栈顶,需要读数据的时候从栈顶开始弹出数据(最后一个数据被第一个读出来)。栈被使用于非常多的地方,例如浏览器中的后退按钮,文本编辑器中的撤销机制。

python算法与数据结构-栈(43)_第1张图片

进栈的时候是1先进,然后是2、3、4、5、6,出栈的时候是先6出,然后是5、4、3、2、1

二、栈中常用的方法

作为一个栈(用stack来表示),最基本的方法有下面几个:

  • stack.push(e): 将元素e添加到S的栈顶

  • stack.pop(): 从栈S中移除并返回栈顶的元素,如果此时栈是空的,那么这个操作将会报错

  • stack.top(): 不移除栈顶元素,但返回栈顶元素,如果此时栈是空的,那么这个操作将会报错

  • stack.is_empty(): 如果栈为空,则返回True,否则返回False

  • len(stack): 返回栈中元素的数量,使用len的特殊方法实现

  • stack.travel()遍历栈里面的元素

三、栈的python代码实现

class Stack():
    """
    以list为基础实现的栈
    """

    def __init__(self):
        self._data = []

    def __len__(self):
        return len(self._data)

    def is_empty(self):
        if len(self._data) == 0:
            return True
        else:
            return False

    def push(self, e):
        self._data.append(e)

    def pop(self):
        if self.is_empty():
            print("栈为空")
            return
        return self._data.pop()

    def top(self):
        if self.is_empty():
            print("栈为空")
            return
        return self._data[-1]
    
    def travel(self):
        for i in range(0,len(self._data)):
            print("%d"%self._data[i])
            

if __name__ == '__main__':
    print("创建栈")
    stack = Stack()
    stack.pop()
    print("验证是否为空:",end="")
    empty = stack.is_empty()
    if empty == True:
        print("空栈")
    else:
        print("不是空")
    print("进栈")
    stack.push(1)
    stack.push(2)
    stack.push(3)
    stack.push(4)
    stack.push(5)
    stack.push(6)
    print("遍历验证进栈")
    stack.travel()
    print("判断是否为空:",end=" ")
    empty = stack.is_empty()
    if empty == True:
        print("空栈")
    else:
        print("不是空")
    print("出栈:",end=" ")
    pop = stack.pop()
    print(pop)
    stack.travel()
    print("验证栈顶元素:",end=" ")
    top =  stack.top()
    print(top)

运行结果为:

创建栈 栈为空 验证是否为空:空栈 进栈 遍历验证进栈 1 2 3 4 5 6 判断是否为空: 不是空 出栈: 6 1 2 3 4 5 验证栈顶元素: 5

四、栈的C语言代码实现

//  main.m
////  Created by 侯垒 on 2019/7/3.
//  Copyright © 2019 可爱的侯老师. All rights reserved.

# include

typedef struct N
{
    int num;
    struct N *next;
}Node;

Node * createNode(int num)
{
    
    Node *node = (Node *)malloc(sizeof(Node));
    node->num = num;
    node->next = NULL;
    return node;
}

Node * createStack()
{
    Node *head = NULL;
    return head;
}

int is_empty(Node *head)
{
    if (head == NULL)
    {
        return 1;
    }
    else
    {
        return 0;
    }
    
}

int length(Node *head)
{
    Node *current = head;
    if (is_empty(head))
    {
        return 0;
    }
    int count = 1;
    while (current->next!=NULL)
    {
        count++;
        current = current->next;
    }
    return count;
}

Node *push(Node *head, int num)
{
    Node *node = createNode(num);
    if (is_empty(head)==1)
    {
        head = node;
    }
    else
    {
        Node *current = head;
        while (current->next!=NULL)
        {
            current = current->next;
        }
        current->next = node;
    }
    return head;
}

Node *pop(Node *head)
{
    if (is_empty(head) == 1)
    {
        printf("站为空");
        return head;
    }
    else
    {
        Node *current = head;
        int len = length(head);
        if (len == 1)
        {
            head = NULL;
        }
        else
        {
            for (int i=0; i2;i++)
            {
                current = current->next;
            }
            current->next = NULL;
        }
        
    }
    return head;
}

int top(Node *head)
{
    if (is_empty(head))
    {
        printf("栈为空");
        return -1;
    }
    return  head->num;
}

void travel(Node *head)
{
    if (is_empty(head) == 1)
    {
        printf("站为空\n");
    }
    else
    {
        Node *current = head;
        int len  = length(head);
        for (int i = 0; i)
        {
            printf("%d ",current->num);
            current = current->next;
        }
        printf("\n");
    }
}


int main(int argc, const char * argv[]) {
  
    printf("创建栈\n");
    Node *head = createStack();
    printf("验证是否为空: ");
    int empty = is_empty(head);
    if (empty == 1)
    {
        printf("栈为空\n");
    }
    else
    {
        printf("栈不为空\n");
        
    }
    printf("验证进栈\n");
    head = push(head, 1);
    travel(head);
    head = push(head, 2);
    head = push(head, 3);
    head = push(head, 4);
    head = push(head, 5);
    head = push(head, 6);
    travel(head);
    printf("验证栈顶元素\n");
    int t = top(head);
    printf("top = %d\n",t);
    
    printf("验证出栈\n");
    head = pop(head);
    travel(head);
    head = pop(head);
    travel(head);
    head = pop(head);
    travel(head);
    head = pop(head);
    travel(head);
    head = pop(head);
    travel(head);
    head = pop(head);
    travel(head);
   
    
    return 0;
}

运行结果为:

创建栈
验证是否为空: 栈为空
验证进栈
1 
1 2 3 4 5 6 
验证栈顶元素
top = 1
验证出栈
1 2 3 4 5 
1 2 3 4 
1 2 3 
1 2 
1 
站为空

 

转载于:https://www.cnblogs.com/Se7eN-HOU/p/11127426.html

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