Final Exam

Final Exam
C++ Programming
NCNU CSIE

Date: January 11th, 2012
Time: 14:10-15:40
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 = 111, b = 0111, c = 0x111;
    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 string
#include <iostream>
using std::cout;

int main()
{
    char name[] = 'Coconut';
    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=2, 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", 72);       // '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:\n";
    for (i=2; i < 20; i++)
    {
        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[] = { 1, 3, 5, 7, 2, 4, 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, 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]) // I am the smallest
        {
            p->next = head;
            head = p;
            continue;
        }

        current = previous = head;
        while (current != NULL && current->value < a[i])
        {
            previous = current;
            current = current->next;
        }
        if (current == NULL)  // I am the largest
        {
            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 = 28;
    int odd = 0;
    int even = 0;

    while (n > 0)
    {
        switch (n % 2)
        {
        case 0:
            even++;
            break;
        case 1:
            odd++;
        } // This "break" statement is omitted.  What will happend?
        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).

// This question comes from NTHU
#include <iostream>
using std::cout;

int f(char *s, char *t)
{
    char *p1, *p2;
    for (p1 = s; *p1; p1++)
    {
        for (p2 = t; *p2; p2++)
            if (*p1 == *p2) break;
        if (*p2 == '\0') break;
    }
    return p1 - s;
}

int main()
{
    cout << f("abccbad", "babc") << '\n';
    return 0;
}

Final Exam C++ Programming NCNU CSIE

Final Exam
C++ Programming
NCNU CSIE