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 = -1;
}

判断栈空：

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

    flag = (s -> top == -1)? 1 : 0; //此处未用if

    return flag;
}

入栈：

void push(struct seqstack *s,x)
{
    s -> top ++;
    if stackfull; //伪
        exit("stack overflow
");    //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!
");
    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!
");
    return s -> top -> data;
}