面試考題-C語言

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最近經歷了殘酷的疲勞面試，從中學習了很多，不管是表達方面還是個人機處方面都有所進步。其中，在面試不乏各式的考題包含C語言、作業系統概念和計組。就幫自己做個紀錄也順便分享一下，等之後有公司了再分享面試心得。

C語言考題

指標

  1. The content of array a?

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    int a[ ]={6,7,8,9,10};
    int *p= a;
    *(p++) +=123;
    *(++p) +=123;

  2. 請問輸出為何?

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    char i[ ] = “Hello”;
    char *p = 1;
    int n = 10;
    printf(“%d %d %d”, sizeof(i), sizeof(p), 		sizeof(n));

  3. 請問輸出為何?

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    int main(){
    	int a[] ={1,2,3,4,5,6};
    	int *ptr = (int*) (&a+1);
    	printf("%d", *(ptr-1));
    }

  4. 請問輸出為何?

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    int main(){
    	int arr[] = {10,20,30,40,50};
    	int *ptr1 = arr;
    	int *ptr2 = arr + 5;
    	printf("%d", (ptr2-ptr1));
    	printf("%d", (char*)ptr2 - (char*)ptr1);
    }

  5. 請問輸出為何?

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    int main(){
    	int arr1[] = {10,20};
    	int arr2[] = {10,20};
    	int arr3[] = {10,20};
    	int *p = arr1;
    	int *q = arr2;
    	int *r = arr3;
    	++*p;
    	*q++;
    	*++r;
    	printf("%d %d %d", arr1[0], arr1[1], *p);
    	printf("%d %d %d", arr2[0], arr2[1], *q);
    	printf("%d %d %d", arr3[0], arr3[1], *r);
    }

  6. 請問輸出為何?

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    void f(int *p, int *q){
    	p = q;
    	*p = 2;
    }

    int i=0, j=1;
    int main(){
    	f(&i, &j);
    	printf("%d %d\n", i, j);
    }

  7. 請問輸出為何?

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    int main(){
    	char s[ ]="0113256";
    	char *p = s;
    	
    	printf("%c", *p++);
    	printf("%c", *(p++));
    	printf("%c", (*p)++);
    	printf("%c", *++p);
    	printf("%c", *(++p));
    	printf("%c", ++*p);
    	printf("%c", ++(*p));
    	printf("\n");
    	printf("%s",s);
    }

  8. 請問輸出為何?

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    int main(){
    	int ref[]={8,4,0,2};
    	int *ptr;
    	int index;
    	for(index=0, ptr=ref; index<2; index++,ptr++)
    		printf("%d %d\n", ref[index], *ptr);
    	(*ptr++);
    	printf("%d %d\n", ref[index], *ptr);
    }

陣列

  1. 請問輸出為何?

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    ine main() {
    	char *str[ ][2] =
    		{ "professor", "Justin" ,
    		  "teacher", "Momor" ,
    		  "student", "Caterpillar"};

    	char str2[3][10] = {"professor", "Justin", "etc"};
    	printf("%s\n", str[1][1]);
    	printf("%c\n",str2[1][1]);
    }

  2. what is final value of cnt?

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    int cnt = 10;
    const char *pc = "welcome";
    while(*pc++)
    	cnt++;

實作題

  1. Write a function that can calculate?
    1*2 + 2**3 + …… + (n-1)*n

  2. 寫一個string compare的function。相同return 0，不同return 1

  3. 寫一個sort演算法

  4. 在一個數值中計算幾個bit為1

  5. 將一個數值的奇偶bit互換

  6. 將一個字串reverse

  7. 給一個連續數列，找出連續最長的1bit

其他

  1. 請問輸出為何？

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    sizeof(byte)? sizeof(float)? sizeof(int)? sizeof(short)? sizeof(short)?

  2. 請問輸出為何?

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    #include <stdio.h>

    union StateMachine {
        char character;
        int number;
        char *str;};

    int main(void) {
        union StateMachine machine;
        machine.number = 1;

        printf("sizeof: %lu\n", sizeof(machine));
        printf("number: %d\n", machine.number);
    }

  3. Write a function which can return the bit content form.
    給一個整數變數a
    (1)設置a的bit3
    (2)清除a的bit3

  4. 請問v為何?

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    unsign long v1 = 0x00001111;
    unsign long v2 = 0x00001202;
    unsign long v;
    v = v1 & (~v2);
    v = v1 | v2;