求栈中的最大值

利用一个辅助的顺序表来

先定义栈和顺序表

typedef struct _Seqlist 
{
    DataType array[MaxNum];
    int len;
}Seqlist,*PSeqlist;

typedef struct _Stack 
{
    DataType array[MaxNum];
    int len;
}Stack,*PStack;

入栈出栈时，都更新顺序表

int PushStack(PStack sta,DataType key,PSeqlist list)
{
    if (sta->len > MaxNum)
    {
        printf("Out of Stack!\n");
        return Empty;
    }
    else
    {
        sta->array[sta->len++] = key;
        if ((list->len > 0) && key > list->array[list->len-1])
        {
            list->array[list->len++] = key;
        }
        else
        {
            list->array[list->len] = list->array[list->len-1];
            list->len++;
        }
    }
    return list->array[list->len-1];
}

int PopStack(PStack sta,PSeqlist list)
{
    if (sta->len < 1)
    {
        printf("Lilk of Stack!\n");
        return Empty;
    }
    else
    {
        int ret;
        sta->array[--sta->len] = 0;
        ret = list->array[--list->len-1];
        return ret; 
    }
}