Midterm Exam (1)

Midterm Exam (1)
C++ Programming
NCNU CSIE

Date: February 22nd, 2013
Time: 08:10-10:00
Open book; turn off computer & mobile phone

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Bitwise Shift Operator (pp.86-88)
#include <iostream>
using std::cout;
using std::endl;

int main()
{
    signed int n = 1;
    int i = 2;
    for (i=0; i<31; i++)
        n <<= 1;
    for (i=0; i<31; i++)
        n >>= 1;
    cout << n << endl;
    return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Arrays of Pointers to Char
#include <iostream>
using std::cout;
using std::endl;

int main()
{
	char* pstr[] = { "Arkansas", "Oklahoma", "Kentucky" };
	cout << **pstr << endl;
	cout << *(pstr + 1) << endl;
	return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Precedence (P.77)
#include <iostream>
using std::cout;
using std::endl;

int main()
{
	char* pstr[] = { "Arkansas", "Oklahoma", "Kentucky" };
	char** p = pstr;	// array name as a pointer
	cout << **p++ << endl;
	cout << *(p + 1) << endl;
	return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// ASCII code of a character
#include <iostream>

void bar(short n)
{
    for (short i=0; i<n; i++)
        printf("%c", 77);       // 'A' == 65
    printf("\n");
    return;
}

int main()
{
    short b[] = { 2, 0, 3, 2, 4, 3 };
    int i;
    for (i=0; i<= 4; i++)
    {
        printf("%2d ", b[i]);
        bar(b[i]);
    }
    return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// nested for-loop
#include <iostream>
using std::cout;
using std::endl;

int main ()
{
     int space;
     int rows;     
	 int star;

    for (rows = 0; rows <9; rows ++)
    {   for (space = 0; space < 8 - rows; space ++)
			cout << " ";
        for (star = 0; star < 8 + rows * 2; star ++)
            cout << "*";
		cout << endl;		
    }     
    return 0;     
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Member function of a class
#include <iostream>
using std::cout;
using std::endl;

class CCircle
{
public:
	int x;
	int y;
	int r;

	void MoveCircle(int x0, int y);
};

int main()
{
	CCircle hut1, hut2;
	hut1.x = 10; hut1.y = 10; hut1.r = 10;
	hut2 = hut1;
	hut2.MoveCircle(50, 70);
	cout << hut2.y << endl;
	return 0;
}

// Do you need to pass by reference?
void CCircle::MoveCircle(int x0, int y)
{
	x = x0; 
	this->y = y;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

#include <iostream>
using std::cout;

void swap(int& i, int &j)
{
    j ^= i; i ^= j; j ^= i;	// eXclusive OR
}

int main()
{
    int data[] = { 3, 1, 4, 1, 5, 9, 2, 6 };
    int i, j;
    for (i=0; i<6; i++)
        for (j=i+1; j<7; j++)
            if (data[i] > data[j])
                swap(data[i], data[j]);
    for (i=0; i<7; i++)
        cout << data[i];
    return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Linked-list
#include <iostream>
using std::cout;

struct Node
{
    int value;
    Node* next;
};

int main()
{
    int a[] = { 3, 1, 5, 4, 0, 6};
    Node* p;
    Node* current;
    Node* previous;
    Node* head = new Node;
        head->value = a[0]; head->next = NULL;
    int i, n;
    n = sizeof(a) / sizeof(a[0]);
    for (i=1; i < n; i++)
    {
        p = new Node;
        p->value = a[i];

        if (head->value < a[i]) 
        {
            p->next = head;
            head = p;
            continue;
        }

        current = previous = head;
        while (current != NULL && current->value > a[i])
        {
            previous = current;
            current = current->next;
        }
        if (current == NULL)  
        {
            previous->next = p;
            p->next = NULL;
        }
        else
        {
            previous->next = p;
            p->next = current;
        }
    }

    p = head;
    while (p)
    {
        cout << p->value;
        p = p->next;
    }
    cout << '\n';
    return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// switch case
#include <iostream>
using std::cout;
using std::endl;
using std::cin;

int main()
{
    int n = 21;
    int odd = 0;
    int even = 0;

    while (n > 0)
    {
        switch (n % 2)
        {
        case 0:
            even++;
            break;
        default:
            odd++;
        } 
        n >>= 1;
    }
    cout << "even=" << even << endl;
    cout << "odd=" << odd << endl;
    return 0;
}

(10%) Determine whether the following code has syntax erros or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

// Pass-by-reference
#include <iostream>
using std::cout;
using std::endl;

void print(int i, int j)
{
    cout << "i = " << i << "\t j = " << j << endl;
}

void swap1(int a, int b)
{   int temp;
    temp = a; a = b; b = temp;
}
void swap2(int &a, int &b)
{   int temp;
    temp = a; a = b; b = temp;
}
void swap3(int a, int& b)
{   int temp;
    temp = a; a = b; b = temp;
}

int main()
{
    int i=2, j=21;
    
    swap2(i,j); print(i,j);
    swap3(i,j); print(i,j);
}

Midterm Exam (1) C++ Programming NCNU CSIE

Midterm Exam (1)
C++ Programming
NCNU CSIE