本文提供了一套针对C程序员的高级测试题目，涵盖了从指针操作到复杂的数据结构及递归算法等内容，旨在评估和提升程序员的技能水平。
Advanced Test in C: The 0x10 Best Questions for C Programmers
http://stevenkobes.com/ctest.html
This test was written by Ashok K. Pathak, a researcher at Bharat Electronics Limited (CRL), Ghaziabad. Ashok has an M.E. from Motilal Nehru Reginal Engineering College, Allahabad, and is the author of a book titled “Advanced Test in C and Embedded System Programming”.
This test appeared as an article on programmersheaven.com. It is reproduced here with modifications, which are as follows:
- Javascript-based scoring and answer display functionality was added.
- Minor errors in questions 3, 13, and 14 are corrected.
- All necessary headers are introduced with
#include. - Declarations of
mainare C99 compliant. - Data type sizes are supplied only where necessary (questions 9 and 14).
- Questions 9, 10, and 12 have more convincing wrong choices.
- Code spacing and indentation are more consistent.
- Spacing of
printfoutput has been corrected in a few places. - All code is syntax highlighted (TextPad-style).
- Minor stylistic adjustments were made.
- Answers are re-worded for clarity, accuracy, and completeness.
If you find any mistakes, please let me know: 
— Steve Kobes, 8/25/04
Jump to question: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1. Consider the following program:
#include
#include
static jmp_buf buf;
int main(void)
{
volatile int b = 3;
if (setjmp(buf) != 0)
{
printf("%d/n", b);
exit(0);
}
b = 5;
longjmp(buf, 1);
}
What is the output of this program?
(a) 3 (b) 5 (c) 0 (d) none of the above
2. Consider the following program:
#include
int main(void)
{
struct node
{
int a;
int b;
int c;
};
struct node s = { 3, 5, 6 };
struct node *pt = &s;
printf("%d/n", *(int*)pt);
return 0;
}
What is the output of this program?
(a) 3 (b) 5 (c) 6 (d) 7
3. Consider the following code segment:
int foo(int x, int n)
{
int val = 1;
if (n > 0)
{
if (n % 2 == 1)
val *= x;
val *= foo(x * x, n / 2);
}
return val;
}
What function of x and n is computed by foo?
(a) xn (b) x × n (c) nx (d) none of the above
4. Consider the following program:
#include
int main(void)
{
int a[5] = { 1, 2, 3, 4, 5 };
int *ptr = (int*)(&a + 1);
printf("%d %d/n", *(a + 1), *(ptr - 1));
return 0;
}
What is the output of this program?
(a) 2 2 (b) 2 1 (c) 2 5 (d) none of the above
5. Consider the following program:
#include
void foo(int[][3]);
int main(void)
{
int a[3][3] = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
foo(a);
printf("%d/n", a[2][1]);
return 0;
}
void foo(int b[][3])
{
++b;
b[1][1] = 9;
}
What is the output of this program?
(a) 8 (b) 9 (c) 7 (d) none of the above
6. Consider the following program:
#include
int main(void)
{
int a, b, c, d;
a = 3;
b = 5;
c = a, b;
d = (a, b);
printf("c=%d ", c);
printf("d=%d/n", d);
return 0;
}
What is the output of this program?
(a) c=3 d=3 (b) c=5 d=3 (c) c=3 d=5 (d) c=5 d=5
7. Consider the following program:
#include
int main(void)
{
int a[][3] = {1, 2, 3, 4, 5, 6};
int (*ptr)[3] = a;
printf("%d %d ", (*ptr)[1], (*ptr)[2]);
++ptr;
printf("%d %d/n", (*ptr)[1], (*ptr)[2]);
return 0;
}
What is the output of this program?
(a) 2 3 5 6 (b) 2 3 4 5 (c) 4 5 0 0 (d) none of the above
8. Consider the following code segment:
#include
int *f1(void)
{
int x = 10;
return &x;
}
int *f2(void)
{
int *ptr;
*ptr = 10;
return ptr;
}
int *f3(void)
{
int *ptr;
ptr = malloc(sizeof *ptr);
return ptr;
}
Which of these functions uses pointers incorrectly?
(a) f3 only (b) f1 and f3 (c) f1 and f2 (d) f1, f2, and f3
9. Consider the following program:
#include
int main(void)
{
int i = 3;
int j;
j = sizeof(++i + ++i);
printf("i=%d j=%d/n", i, j);
return 0;
}
What is the output of this program on an implementation where int occupies 2 bytes?
(a) i=4 j=2 (b) i=3 j=2 (c) i=5 j=2 (d) the behavior is undefined
10. Consider the following program:
#include
void f1(int*, int);
void f2(int*, int);
void (*p[2])(int*, int);
int main(void)
{
int a = 3;
int b = 5;
p[0] = f1;
p[1] = f2;
p[0](&a, b);
printf("%d %d ", a, b);
p[1](&a, b);
printf("%d %d/n", a, b);
return 0;
}
void f1(int *p, int q)
{
int tmp = *p;
*p = q;
q = tmp;
}
void f2(int *p, int q)
{
int tmp = *p;
*p = q;
q = tmp;
}
What is the output of this program?
(a) 5 5 5 5 (b) 3 5 3 5 (c) 5 3 3 5 (d) none of the above
11. Consider the following program:
#include
void e(int);
int main(void)
{
int a = 3;
e(a);
putchar('/n');
return 0;
}
void e(int n)
{
if (n > 0)
{
e(--n);
printf("%d ", n);
e(--n);
}
}
What is the output of this program?
(a) 0 1 2 0 (b) 0 1 2 1 (c) 1 2 0 1 (d) 0 2 1 1
12. Consider the following code segment:
typedef int (*test)(float*, float*);
test tmp;
What is the type of tmp?
(a) function taking two pointer-to-float arguments and returning pointer to int (b) pointer to int (c) pointer to function taking two pointer-to-float arguments and returning int (d) none of the above
13. Consider the following program:
#include
int main(void)
{
char p;
char buf[10] = {1, 2, 3, 4, 5, 6, 9, 8};
p = (buf + 1)[5];
printf("%d/n", p);
return 0;
}
What is the output of this program?
(a) 5 (b) 6 (c) 9 (d) none of the above
14. Consider the following program:
#include
void f(char**);
int main(void)
{
char *argv[] = { "ab", "cd", "ef", "gh", "ij", "kl" };
f(argv);
return 0;
}
void f(char **p)
{
char *t;
t = (p += sizeof(int))[-1];
printf("%s/n", t);
}
What is the output of this program on an implementation where int and all pointer types occupy 2 bytes?
(a) ab (b) cd (c) ef (d) gh
15. Consider the following program:
#include
#include
int ripple(int n, ...)
{
int i, j, k;
va_list p;
k = 0;
j = 1;
va_start(p, n);
for (; j < n; ++j)
{
i = va_arg(p, int);
for (; i; i &= i - 1)
++k;
}
return k;
}
int main(void)
{
printf("%d/n", ripple(3, 5, 7));
return 0;
}
What is the output of this program?
(a) 7 (b) 6 (c) 5 (d) 3
16. Consider the following program:
#include
int counter(int i)
{
static int count = 0;
count = count + i;
return count;
}
int main(void)
{
int i, j;
for (i = 0; i <= 5; i++)
j = counter(i);
printf("%d/n", j);
return 0;
}
What is the output of this program?
(a) 10 (b) 15 (c) 6 (d) 7
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