零零总总的面试题（1）

最新推荐文章于 2019-06-29 20:52:23 发布

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最新推荐文章于 2019-06-29 20:52:23 发布

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FROM:qitian0008(http://blog.youkuaiyun.com/qitian0008);

一. 问题描述：两个数组a[N]，b[N]，其中A[N]的各个元素值已知，现给b[i]赋值，b[i] = a[0]*a[1]*a[2]...*a[N-1]/a[i]；
要求：
1.不准用除法运算
2.除了循环计数值，a[N],b[N]外，不准再用其他任何变量（包括局部变量，全局变量等）

3.满足时间复杂度O（n），空间复杂度O（1）

int main(int argc, char* argv[])
{
	int i;
	int a[10] = {1, 2, 1, 2, 1, 2, 1, 2, 1, 2};
	int b[10];
	
	b[0] = 1;
	for(i = 1; i < 10; i++)
	{
		b[0] *= a[i - 1];
		b[i] = b[0];
	}
	b[0] = 1;
	for(i = 8; i > 0; i--)
	{
		b[0] *= a[i + 1];
		b[i] *= b[0];
	}
	b[0] *= a[1];//注意哦亲
	
	for(i = 0; i < 10; i++)
	{
		cout << b[i] << " ";
	}
	cout << endl;
	
	return 0;
}

二. 二分查找

public int binarySearch(int[] dataset, int data) {
              int beginIndex = 0;
              int endIndex = dataset.length - 1;
              int midIndex = -1;
              if (data < dataset[beginIndex] || data > dataset[endIndex]|| beginIndex > endIndex)//这个也是相当的重要
                     return -1;
              while (beginIndex <= endIndex) {
                     midIndex = (beginIndex + endIndex) >>> 1; //相当于midIndex = (beginIndex + endIndex) / 2，但是效率会高些
                     if (data < dataset[midIndex]) {
                            endIndex = midIndex - 1;
                     } else if (data > dataset[midIndex]) {
                            beginIndex = midIndex + 1;
                     } else {
                            return midIndex;
                     }
              }
              return -1;
       }

三. 字符串翻转

四.

1、计数排序；

2、堆排序；

3、大数据量的处理；

4、快速排序；

5、两个链表的公共节点；

6、一个单链表，不知道头指针，只知道中间元素i的指针，现在删除指针i指向的元素；

7、单链表的反转。

五. 下面的C++代码，哪个是正确的？

A:
int *f()
{
	int a[3]={4,2,3};
	return a;
}

B:
void f3(int * ret)
{
	int a[3]={1,2,3};
	ret=a;
	return;
}

C:
vector<int> f()
{
	vector<int> v(3);
	return v;
}

D:
int f4()
{
	int *a=new int(3);
	return *a;
}

E: None of above

这个选择C。为什么？

以为vector有自动析构的功能。所以不用我们来释放他申请的空间。故不会造成内存的泄露！

In the following，at least one correct answer to each question

1. Suppose that a selection sort of 80 items has completed 32 iterations of the main loop.How many items are now guaranteed to be in their final spot(never to be moved again?)

A. 16

B. 31

C. 32

D. 39

E. 40

Answer：C

2. Which synchronization mechanism(s) is/are used to avoid race conditions among processed/threads in operating systems?

A. Mutex

B. Mailbox

C.Semaphore

D. Local procedure call

Answer：AC

四种进程同步的方法（Mailbox只能通信，不能同步？）：

1、临界区:通过对多线程的串行化来访问公共资源或一段代码，速度快，适合控制数据访问。

2、互斥量:为协调共同对一个共享资源的单独访问而设计的。

3、信号量:为控制一个具有有限数量用户资源而设计。

4、事件:用来通知线程有一些事件已发生，从而启动后继任务的开始。

3. There is a sequence of n numbers 1,2,3,...,n and a stack which can keep m numbers at most.Push the n numbers into the stack following the sequence and pop out randomly.Suppose n is 2 and m is 3,the output sequence may be 1,2 or 2,1, so we get 2 different sequences. Suppose n is 7 and m is 5,please choose the output sequences of the stack.

A. 1,2,3,4,5,6,7

B. 7,6,5,4,3,2,1

C. 5,6,4,3,7,2,1

D. 1,7,6,5,4,3,2

E. 3,2,1,7,5,6,4

Answer：AC

4. What is the result of binary number 01011001 after multiplying by0111001 and adding1101110?

A. 0001010000111111

B. 0101011101110011

C. 0011010000110101

Answer：A

5. What is output if you compile and execute the following c code?

void main()

{

int i=11;

int const *p=&i;

p++;

printf("%d",*p);

}

A. 11

B. 12

C. Garbage value

D. Compiler error

E. None of above

Answer：C

6. Which of following C++ code is correct:

A. int f()

{

int *a = new int(3);

return *a;

}

B. int *f()

{

int a[3] = {1,2,3};

return a;

}

C. vector<int> f()

{

vector<int> v(3);

return v;

}

D. void f(int *ret)

{

int a[3]={1,2,3};

ret = a;

return;

}

Answer：C

其它会有野指针，导致内存泄露

7. Given that the 180-degree rorated image of a 5-digit number is another 5-digit number and the difference between the number is 78633, what is the original 5-digit number?

A. 60918

B. 91086

C.18609

D.10968

E. 86901

Answer：D

8. Which of the following statements are ture?

A. We can create a binary tree from given inorder and preorder traversal sequences.

B. We can create a binary tree from given preorder and postorder traversal sequences.

C. For an almost sorted array, Insertion sort can be more effective than Quicksort.

D. Suppose T(n) is the runtime of resolving a problem with n elements, T(n)=O(1) if n=1; T(n)=2*T(n/2)+O(n) if n>1; so T(n) is O(n*logn).

E. None of above.

Answer：ACD

9. Which of the following statements are true?

A. Insertion sort and bubble sort are not efficient for large data sets.

B. Quick sort makes O(n^2) comparisons in the worst case .

C. There is an array:7,6,5,4,3,2,1. If using selection sort(ascending), the number of swap operation is 6.

D. Heap sort uses two heap operations: insertion and root deletion.

E. None of above.

Answer：ABD

10. Assume both x and y are integers ,which one of the following returns the minimum of the two integers?

A. y^((x^y)&-(x<y)).

B. y^(x^y).

C. x^(x^y)

D. (x^y)^(y^x)

E. None of above

Answer：A

11. The Orchid Pavilion(兰亭集序) is well known as the top of "行书" in history of Chinese literature. The most fascinating sentence is "Well I know it is a lie to say that life and death is the same thing and that longevity and early death make no difference Alas!"("固知一生死为虚诞，齐彭殇为妄作。"). By counting the characters of the whole content (in Chinese version), the result should be 391(including punctuation). For these charaters written to a text file ,please select the possible size without any data corrupt.

A. 782 bytes in UTF-16 encoding

B. 784 bytes in UTF-16 encoding

C. 1173 bytes in UTF-8 encoding

D. 1176 bytes in UTF-8 encoding

E. None of above

Answer：BCD

UTF-16两字节表示一个汉字，有Big Endian和Little Endian两种，必须要加BOM两字节。UTF-8通常三字节一个汉字，有加BOM和不加BOM两种方式。

12. Fill the blanks inside class definition

Class Test

{

public:

_____ int a;

_____ int b;

public:

Test::Test(int _a, int _b):a(_a)

{

b = _b;

}

};

int Test::b;

int _tmain(int argc, _TCHAR * argv[])

{

Test t1(0, 0), t2(1, 1);

t1.b = 10;

t2.b = 20;

printf("%u %u %u %u", t1.a ,t1.b ,t2.a, t2.b);

return 0;

}

Running result: 0 20 1 20

A. static/const

B. const/static

C. --/static

D.const static/static

E. None of the above

Answer：BC

13. A 3-order B-tree has 2047 key words, what is the maximum height of the tree?

A. 11 B. 12 C. 13 D. 14

Answer：A

定理9.1 若n≥1，m≥3，则对任意一棵具有n个关键字的m阶B-树，其树高h至多为：
logt((n+1)/2)+1。
这里t是每个(除根外)内部结点的最小度数，即

14. In C++, which of the following keyword(s) can be used on both a variable and a function?

A. static B. virtual C. extern D.inline E. const

Answer：ACE

15. what is the result of the following program?

char * f( char * str, char ch)

{

char * it1 =str;

char * it2=str;

while(* it2 != '\0' )

{

while (* it2 ==ch)

{

it2++;

}

*it1++ = *it2++;

}

return str;

}

void main( int argc, char *argv[])

{

char * a = new char[10];

strcpy(a, "abcdcccd");

count << f(a, 'c');

}

A. abdcccd

B. abdd

C. abcc

D. abddcccd

E. Access violation

Answer：D

16. Consider the following definition of a recursive function ,power ,that will perform exponentiation.

int power(int b, int e)

{

if(e==0) return 1;

if(e%2 == 0) return power(b*b, e/2);

return b*power(b*b,e/2);

}

A. logarithmic

B. linear

C. quadratic

D. exponentical

Answer：A

17.Assume a full deck of cards has 52 cards, 2 black suits(spade and club) and 2 red suits(diamond and heart). If you are given a full deck, and half deck(with 1 red suit and a black suit), what's the possiblility for each one getting 2 red cards if taking 2 cards?

A. 1/2,1/2 B. 25/102,12/50 C. 50/51, 24/25 D. 25/51,12/25 E. 25/51,1/2

Answer：B

18. There is a stack and a sequence of n numbers (i.e. 1,2,3,...,n). Push the n numbers into the stack following the sequence and pop out randomly. How many different sequences of the n number we may get? Suppose n is 2,the output sequence may 1,2 or 2,1, so we get 2 different sequences.

A. C_2n^n

B. C_2n^n-C_2n^(n+1)

C. ((2n)!)/(n+1)n!n!

D. n!

E. none of the above

Answer：B?

19. Longest Increasing Subsequence(LIS) means a sequence containing some elements in another sequence by the same order, and the values of elements keep increasing.

For example, LIS of (2,1,4,2,3,7,4,6) is (1,2,4,6), and its LIS length is 5.

Considering an array with N element ,what is the lowest time and space complexity to get the length of LIS?

A. Time:N^2, Space:N^2;

B. Time:N^2, Space:N;

C. Time:NlogN, Space:N;

D. Time:N, Space:N;

E. Time:N, Space:C

Answer：C

20.What is the output of the follow piece of C++ code?

#include <iostream>

using namespace std;

struct Item

{

char c;

Item *next;

};

Item * Routine1( Item* x)

{

Item *prev = NULL,

curr = x;

while(curr)

{

Item *next = curr->next;

curr->next = prev;

prev = curr;

curr = next;

}

return prev;

}

void Routine2(Item *x)

{

Item *curr = x;

while(curr)

{

cout<<curr->c<<" ";

curr = curr->next;

}

void _tmain(void)

{

Item *x,

d = {'d', NULL},

c = {'c', &d},

b = {'b', &c},

a = {'a', &b};

x = Routine1(&a);

Routine2(x);

}

A. c b a d B. b a d c C. d b c a D. a b c d E. d c b a

Answer：E

六.

static int ack(int m,int n){
	if(m==0){
		return n+1;
	}
	else if(n==0){
		return ack(m-1,1);
	}
	else{
		return ack(m-1,ack(m,n-1));
	}
}

求ack(2,29)是多少？

我们来看下 ack(1,n)=ack(0,ack(1,n-1))=ack(1,n-1)+1=...=ack(1,0)+n

我们推知ack(1,0)=2

故 ack(1,n)=n+2；

ack(2,n)=ack(1,ack(2,n-1))=ack(2,n-1)+2=...=ack(2,0)+2n

我们推知ack(2,0)=3

故ack(2,n)=2n+3

所以上面的结果就是 2*29+3=61

七.360

1、不用库函数，写出atoi的实现过程

关于这题，我们需要注意的有以下几点：

1）根据字符串第一个字符，判断正负数；

2）判断每一个字符是否是数字；

3）判断是否会越界。

2.定义 char a[]="hello";

char *s="hello";

那么下面的写法对吗：

a[1]='H';

*s++='H';

char a[]="hello"; //将字符串存储在a开辟的栈存储区域，即a[0]='h',....a[6]='\0',栈的存储区是可读可修改的。
char *s="hello"; //"hello“是存储在字符串常量存储区域，s为其收地址，该区域是不能修改的。
那么下面的写法对吗：
a[1]='H'; //正确
*s++='H'; //错误！

3.单链表的逆序

4.大数据量的问题：一亿大小的文件，里面有N行记录，每行最长100字符，内存大小1M，给出合理的方式，求出里面重复率最大的那个记录