Midterm Exam (1)

Midterm Exam (1)
C++ Programming
NCNU CSIE

Date: February 24th, 2012
Time: 09:10-11:00
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).

// printf()
#include <iostream>
using std::cout;

int main()
{
    short a = 224, b = 0224, c = 0x224;
    printf("%d\t%o\t%x\n", a, a, a);
    printf("%d\t%o\t%x\n", b, b, b);
    printf("%d\t%o\t%x\n", c, c, c);
    // if you don't specify the width,
    // it will be aligned to the left
    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).

// character pointer
#include <iostream>
using std::cout;

int main()
{
    char *name = "Europe";
    cout << sizeof(name) << '\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).

// Precedence (P.77)
#include<iostream>
using std::cout;
using std::endl;
int main()
{
    int a=1, n=3;

    int sum=0;
    while ( --n >= 1)
    {
        sum+=a;
        a = (a * 10) + a % 10;
   }
   cout << sum << 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", 73);       // 'A' == 65
    printf("\n");
    return;
}

int main()
{
    short b[] = { 5, 4, 3, 5, 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;

int main()
{
    bool prime;
    int i, j;
    cout << "These are prime numbers:\n2 ";
    for (i=3; i < 20; i+=2)
    {
        prime = true;
        for (j=3; j < i; j++)
            if (i / j * j == i)         // Is i dividable by j?
                prime = false;
        if (prime)
            cout << 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).

// array
#include <iostream>
using std::cout;

int main()
{
    const int MAX = 100;
    bool prime[MAX] = { false, false };
    int i, j, count = 0;
    for (i=2; i < MAX; i++)
        prime[i] = true;
    for (i=2; i < MAX; i++)
        for (j=i*2; j < MAX; j+=i)
            prime[j] = false;
    for (i=2; i < MAX; i++)
    {
        if (prime[i])
        {
            cout << i << '\t';
            if (count++ % 5 == 0) 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).

#include <iostream>
using std::cout;

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

int main()
{
    int data[] = { 2, 4, 6, 1, 3, 5, 7 };
    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, 5, 1, 7, 2, 4, 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).

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

int main()
{
    int n = 24;
    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=24;
    swap1(i,j); print(i,j);
    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