指针笔试面试题讲解

指针笔试面试题讲解 读代码写出结果

---

1.

#include
int main()
{
    int a[4] = { 1, 2, 3, 4 };
	int *ptr1 = ( int * )(&a + 1);
	int *ptr2 = (int *)((int)a + 1);
	printf("%x %x", ptr1[-1], *ptr2); 

	return 0;
}

分析一下这串代码： 

 在这里，我们分析清楚了ptr1 和ptr2指向的是哪里。

接下来我们看看打印的这两个是什么样子的东西。

 看打印结果：

2.

#include
int main()
{
    char *c[] = { "ENTER", "NEW", "POINT", "FIRST" };
	char **cp[] = { c + 3, c + 2, c + 1, c };
	char ***cpp = cp;

	printf("%sn", **++cpp);
	printf("%sn", *--*++cpp + 3);
	printf("%sn", *cpp[-2] + 3);
	printf("%sn", cpp[-1][-1] + 1);

    return 0;
}	

这段代码的结果是什么呢？

 

 来看一下最后的打印结果~~

3.

#include
int main()
{
    int a[3][2] = { (0, 1), (1, 2), (2, 3) };
	int *p;
	p = a[0];
	printf("%d", p[0]);

    return 0;
}

来看看打印结果

4.

#include
int main()
{
    int a[5][5];
	int(*p)[4];
	p = (int(*)[4])a;
	printf("%p %dn", &p[4][2] - &a[4][2], &p[4][2] - &a[4][2]);

    return 0;
}

来看一下打印结果

5.

#include
int main()
{
    int aa[2][5] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	int *ptr1 = (int *)(&aa + 1);
	int *ptr2 = (int *)(*(aa + 1));
	printf("%d %dn", *(ptr1 - 1), *(ptr2 - 1));

    return 0;
}

 来看一下运行结果

6.

int main()
{
	int a[] = { 1, 2, 3, 4 };
	printf("%dn", sizeof(a)); 
	printf("%dn", sizeof(a + 0));  
	printf("%dn", sizeof(*a));  
	printf("%dn", sizeof(a + 1)); 
	printf("%dn", sizeof(a[1])); 
	printf("%dn", sizeof(&a));
	printf("%dn", sizeof(*&a));
	printf("%dn", sizeof(&a + 1)); 
    printf("%dn", sizeof(&a[0]));
	printf("%dn", sizeof(&a[0] + 1));

    return 0;
}

---

字符串1 

#include
#include
int main()
{
    char arr[] = { 'a', 'b', 'c', 'd', 'e', 'f' }; 

	printf("%dn", sizeof(arr));  
	printf("%dn", sizeof(arr + 0));  
	printf("%dn", sizeof(*arr));  
	printf("%dn", sizeof(arr[1])); 
	printf("%dn", sizeof(&arr + 1));  
	printf("%dn", sizeof(&arr[0] + 1)); 

    printf("%dn", strlen(arr));
	printf("%dn", strlen(arr+0));
	printf("%dn", strlen(*arr));
	printf("%dn", strlen(arr[1]));
	printf("%dn", strlen(&arr));
	printf("%dn", strlen(&arr + 1));
	printf("%dn", strlen(&arr[0] + 1));

    return 0;
}    

 

 

 打印结果

---

字符串2

#include
#include
int main()
{
    char arr[] = "abcdef"; 

	printf("%dn", sizeof(arr));  
	printf("%dn", sizeof(arr + 0));  
	printf("%dn", sizeof(*arr));  
	printf("%dn", sizeof(arr[1])); 
	printf("%dn", sizeof(&arr + 1));  
	printf("%dn", sizeof(&arr[0] + 1)); 

    printf("%dn", strlen(arr));
	printf("%dn", strlen(arr+0));
	printf("%dn", strlen(*arr));
	printf("%dn", strlen(arr[1]));
	printf("%dn", strlen(&arr));
	printf("%dn", strlen(&arr + 1));
	printf("%dn", strlen(&arr[0] + 1));

    return 0;
}    

 打印结果

 

---

指针

#include
int main()
{
    char *p = "abcdef";
	
	printf("%dn", sizeof(p)); 
	printf("%dn", sizeof(p + 1)); 
	printf("%dn", sizeof(*p)); 
	printf("%dn", sizeof(p[0])); 
	printf("%dn", sizeof(&p));  
	printf("%dn", sizeof(&p + 1)); 
	printf("%dn", sizeof(&p[0] + 1)); 

	printf("%dn", strlen(p));
	printf("%dn", strlen(p + 1));
	printf("%dn", strlen(*p)); 
	printf("%dn", strlen(p[0])); 
	printf("%dn", strlen(&p));
	printf("%dn", strlen(&p+1));
	printf("%dn", strlen(&p[0] + 1));

    return 0;
}	

来看打印结果

 

---

二维数组

 

#include
int main()
{
    int a[3][4] = { 0 };

	printf("%dn", sizeof(a)); 
	printf("%dn", sizeof(a[0][0])); 
	printf("%dn", sizeof(a[0]));      
	printf("%dn", sizeof(a[0]+1));
	printf("%dn", sizeof(*(a[0]+1)));  
	printf("%dn", sizeof(a+1));     
	printf("%dn", sizeof(*(a+1))); 
	printf("%dn", sizeof(&a[0] + 1));
	printf("%dn", sizeof(*(&a[0]+1))); 
	printf("%dn", sizeof(*a));	 		
	printf("%dn", sizeof(a[3]));	

    return 0;
}

 打印结果：

 

over~~~