stack note

参考 http://www.cnblogs.com/java06/archive/2012/10/16/3122428.html

1，顺序栈

定义栈：

 #define stacksize 1000;
 typedef int datatype;

 struct seqstack
 {
     datatype data[stacksize];
     int top;
 };

置栈空：

 void initstack(struct seqstack *s)
 {
     s -> top = -;
 }

判断栈空：

 int stackempty(struct seqstack *s)
 {
     int flag;

     flag = (s -> top == -)?  : ; //此处未用if

     return flag;
 }

入栈：

 void push(struct seqstack *s,x)
 {
     s -> top ++;
     if stackfull; //伪
         exit("stack overflow\n");    //数组溢出

     s -> data[s -> top] = x;
 }

2，链栈

定义栈：

 typedef struct stacknode
 {
     datatype data;
     struct stacknode *next;
 }stacknode;

 typedef struct
 {
     stacknode *top;
 }linkstack;

置空：

 void initstack(linkstack *s)
 {
     s -> top = NULL;
 }

判栈空：

 void initstack(linkstack *s)
 {
     s -> top = NULL;
 }

入栈:

 void push(linkstack *s, datatype x)
 {
     struct stacknode *p;
     p = malloc(sizeof(struct stacknode));
     p -> data = x;
     p -> next = s -> top;
     s -> top = p;
 }

出栈：

 datatype pop(linkstack *s)
 {
     datatype x;
     struct stacknode *p = s -> top;
     if(stackempty(s))
         exit("stack is empty!\n");
     x = p -> data;
     s -> top = p -> next;
     free(p);
     return x;
 }

取栈顶：

 datatype stacktop(linkstack *s)
 {
     if(stackempty(s))
         exit("stack is empty!\n");
     return s -> top -> data;
 }