数据结构代码及解析-----栈

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <malloc.h>
  4 
  5 typedef struct Node//定义结点
  6 {
  7     int data;
  8     struct Node *pNext;
  9 }NODE, *PNODE;
 10 
 11 typedef struct Stack//定义栈，栈相当于一个箱子;共有2个结点，一个表示箱顶一个表示箱底
 12 {
 13     PNODE pTop;//箱顶
 14     PNODE pBottom;//箱底
 15 }STACK, *PSTACK;
 16 
 17 void init(PSTACK pS)
 18 {
 19     pS->pTop = (PNODE)malloc(sizeof(NODE));//先造出一个空栈
 20     if (NULL == pS->pTop)
 21     {
 22         printf("动态内存分配失败!\n");
 23         exit(-1);
 24     }
 25     else
 26     {
 27         pS->pBottom = pS->pTop;
 28         pS->pBottom->pNext = NULL;//或使用pS->pTop->pNext = NULL
 29         //因为他们刚开始指向同一个地方---箱底,只要箱底的指针域为空就行了
 30     }
 31 }
 32 
 33 void push(PSTACK pS, int val)
 34 {
 35     PNODE pNew = (PNODE)malloc(sizeof(NODE));//创建一个新的结点放到栈里
 36     if (NULL == pNew)
 37     {
 38         printf("动态内存分配失败!\n");
 39         exit(-1);
 40     }
 41 
 42     pNew->data = val;
 43     pNew->pNext = pS->pTop;
 44     pS->pTop = pNew;
 45 
 46     return;
 47 }
 48 
 49 void traverse(PSTACK pS)//遍历输出
 50 {
 51     PNODE p = pS->pTop;//注意一定要用p临时存放箱顶的结点指针,不然结束后箱顶的结点指针就变了---会影响其他的函数执行
 52     
 53     while (p != pS->pBottom)//当p == pS->pBottom时结束, 此时p已经变成了pS->pBottom箱底
 54     {
 55         printf("%d  ", p->data);
 56         p = p->pNext;
 57     }
 58     putchar(10);
 59 
 60     return;
 61 }
 62 
 63 bool empty(PSTACK pS)
 64 {
 65     if (pS->pTop == pS->pBottom)
 66     {
 67         return true;
 68     }
 69     else
 70         return false;
 71 }
 72 //把pS所指向的栈出栈一次,并把出栈的元素存入pVal所指向的变量
 73 bool pop(PSTACK pS, int *pVal)
 74 {
 75     if (empty(pS))
 76     {
 77         return false;
 78     }
 79     else
 80     {
 81         PNODE r = pS->pTop;
 82         *pVal = r->data;
 83         pS->pTop = r->pNext;
 84         
 85         free(r);
 86         r = NULL;
 87     }
 88 
 89     return true;
 90 }
 91 
 92 
 93 void clear(PSTACK pS)//清空--释放内存
 94 {
 95     if (empty(pS))
 96         return;
 97     else
 98     {
 99         PNODE p = pS->pTop;
100         PNODE q = NULL;
101 
102         while (p != pS->pBottom)
103         {
104             q = p->pNext;
105             free(p);
106             p = q;//结束时p(pS->pTop)已经指向了pS->pBottom箱底,但pS->pTop的内容并不是空结点的
107         }
108 
109         pS->pTop = pS->pBottom;//所以在清空的时候, 要将pS->pTop的数据域也为空
110     }
111 }
112 
113 int main(void)
114 {
115     int val;
116     STACK S;
117     init(&S);
118     
119     push(&S, 1);
120     push(&S, 2);
121     push(&S, 3);
122     push(&S, 4);
123     push(&S, 5);
124     traverse(&S);
125 
126     pop(&S, &val);//只出栈一次
127     printf("你出栈的结点的数据域存储的数是:%d\n", val);
128     traverse(&S);
129 
130     clear(&S);
131     traverse(&S);//没有的话会空一行
132 
133     return 0;
134 }