interview C/C++14

普天C++笔试题解答  

普天C++笔试题解答

1．实现双向链表删除一个节点P，在节点P后插入一个节点，写出这两个函数。

编写了一个完整的可运行程序,其中del_node和insert两个函数分别为题目中要求的两个函数,

其余部分是用来测试这两个函数的.

#include 
#include 
#include 

struct tag_Node {
    struct tag_Node *prev;
    struct tag_Node *next;
    int		value;
};

typedef struct tag_Node Node;
typedef Node DList;

DList *head = NULL;
DList *old_head = NULL;  /* 保存头结点的指针 */

Node *append_node(int n)
{
    Node *p = (Node *)malloc(sizeof(Node));

    if (!p) {
        printf("memory alloc failure!\n");
        exit(1);
    }

    p->value = n;

    if (!head) {
		/* now q contain the address of head */
        old_head = head = p;
        head->prev = 0;
        head->next = 0;
    }

    head->next = p;
    p->prev = head;
    p->next = NULL;
    head = p;

    return p;

}

/* delete a node from double linked list */
void del_node(Node *p)
{
    p->prev->next = p->next;
    p->next->prev = p->prev;

    printf("Node  %d has been deleted!\n", p->value);
    free(p);

}

/* insert a new node after Node p */
Node* insert(Node *p, int n)
{

    Node *new_node = (Node*)malloc(sizeof(Node));
    if (!new_node) {
        printf("memory alloc failure!\n");
        exit(1);
    }

    new_node->value = n;


    new_node->next = p->next;
    p->next->prev = new_node;

    new_node->prev = p;
    p->next = new_node;

    printf("Node %d has been inserted\n", new_node->value);
    return new_node;

}

void print()
{
    Node *p = old_head;

    printf("( ");
    while (p)
    {
        printf("%d, ", p->value);
        p = p->next;
    }

    printf(")\n");
}

void free_all()
{
    Node *p = old_head;
    Node *q;
    while (p)
    {
        q = p;
        p = p->next;
        free(q);
    }

    printf("memory has been freed!\n");
}

int main()
{
    Node *p, *q;

    append_node(3);
    append_node(4);

    p = append_node(5);

    append_node(0);

    q = append_node(1);

    append_node(2);

    print(old_head);

    insert(p, 6);
    print(old_head);

    del_node(q);
    print(old_head);

    free_all();

    return 0;
}

2．写一个函数，将其中的\t都转换成4个空格。

/* 此程序将源程序文件中所有的'\t'转换成4个空格 ,并另存为expanded.c*/

#include 
#include 

int expand_tab()
{
  FILE *fp, *fp2;
  int c;
  char *r_name = "expanded.c";

  if ((fp = fopen(__FILE__, "r")) == NULL)
    {
      perror("file open error");
      exit(1);

    }

  if ((fp2 = fopen(r_name, "w")) == NULL)
    {
      perror("output file open error");
      exit(2);
    }

  while ((c = fgetc(fp)) != EOF)
    {
      if (c == '\t')
        {
          /* '\t' is replaced with 4 spaces */
          fputs("    ", fp2);
          continue;
        }

      fputc(c, fp2);
    }

  fclose(fp);
  fclose(fp2);

  return 0;
}


int main()
{
  int rval = expand_tab();
  if (!rval)
    printf("expand successfully!\n");
  else if (rval == 1)
    printf("error occured in %s!\n", __FILE__);
  else if (rval == 2)
    printf("error occured in tempfile\n");
  else
    printf("unknown error!\n");

  return 0;
}

3．Windows程序的入口是哪里？写出Windows消息机制的流程。 

入口点是WinMain函数. 

4．如何定义和实现一个类的成员函数为回调函数？ 

  将成员函数定义为static

5．C++里面是不是所有的动作都是main()引起的？如果不是，请举例。

全局对象和全局对象的构造函数是在main函数之前执行的。

6．C++里面如何声明const void f(void)函数为C程序中的库函数？

使用extern "C"连接指令, extern "C" const void f(void);

 

7．下列哪两个是等同的 

int b; 

A const int* a = &b; 

B const* int a = &b; 

C const int* const a = &b; 

D int const* const a = &b; 

C和D是等同的,将b的地址赋给一个指向const int对象的常指针.

A的=号左边为一个指向const int对象的指针. B的=号左边为一个指向int型对象的常指针.

8．内联函数在编译时是否做参数类型检查？ 

会做类型检查的,只不过内联函数是在调用点处展开代码,省去了函数调用时候的开销,

但是也可能会带来代码体积变大的问题.

void g(base & b){ 

b.play; 

} 

void main(){ 

son s; 

g(s); 

return; 

}