Self Test 2: Chapter 2, Flow of Control

What is the output of this code?


    1	#include <iostream>
    2	using namespace std;
    3	
    4	int main()
    5	{
    6	  int i;
    7	
    8	  i = 0;
    9	  while( i < 5 ) {
   10	    cout << "A";
   11	    i++;
   12	  }
   13	  return 0;
   14	}

AAAA
AAAAA
A
A
A
A
A
A
A
A
A

next prev start

What is the output of this code? (Note the two slight changes from the previous problem.)


    1	#include <iostream>
    2	using namespace std;
    3	
    4	int main()
    5	{
    6	  int i;
    7	
    8	  i = 1;
    9	  while( i < 5 ) {
   10	    cout << "A" << endl;;
   11	    i++;
   12	  }
   13	  return 0;
   14	}

AAAA
AAAAA
A
A
A
A
A
A
A
A
A

next prev start

There is no syntax error below (it compiles), but it does not do what it claims. What is the error?


    1	#include <iostream>
    2	
    3	using namespace std;
    4	
    5	int main()
    6	{
    7	  int sum;
    8	  int i;
    9	  int n;
   10	  
   11	  cout << "This program will compute the sum 1 + 2 + ... + n" << endl;
   12	  cout << "\nEnter a value for n: ";
   13	  cin >> n;
   14	  
   15	  sum = 0;
   16	  while( i <= n ) {
   17	    sum += i;
   18	    i++;
   19	  }
   20	
   21	  cout << "1 + 2 + ... + " << n << " = " << sum << endl;
   22	
   23	  return 0;
   24	}

sum should be initialized to 1.
i should be initialized to 1.
sum += i; should be sum = sum + i;
i++ should be ++i

next prev start

The following code also compiles without errors, but contains a serious error. What is it?


#include <iostream>

using namespace std;

int main()
{
  int capacity;
  cout << "This program will determine the largest value of n"
       << "\nsuch that 1 + 2 + 3 + ... + n < capacity" << endl;
  cout << "\nEnter a value for capacity > 1: ";
  cin >> capacity;
  if (capacity <= 1) {
    cout << "The capacity  must be > 1" << endl;
    exit(0);
  }

  int sum = 0;
  int n = 1
  while( sum + n < capacity ) {
    sum += n;
  }
  cout << "The largest value of n such that 1 + 2 + 3 + ... + n < " 
       << capacity << " is " << n - 1<< endl;

  return 0;
}

The loop condition sum + n < capacity should be sum < capacity
The initial value of n should be 0.
The statement in the loop body, sum += n; should be sum += n++;
The statement in the loop body, sum += n; should be sum += ++n;

next prev start

What is the output of the code below as written and what would the output be if lines 10 and 11 were interchanged?


    1	#include <iostream>
    2	
    3	using namespace std;
    4	
    5	int main()
    6	{
    7	  int sum = 0;
    8	  int k = 1;
    9	  while (k < 4) {
   10	    sum += k;
   11	    k++;
   12	  }
   13	  cout << sum << endl;
   14	
   15	  return 0;
   16	}

4 and 4
6 and 6
4 and 7
6 and 9

next prev start

Which for loop below is equivalent to this code using a while loop:


  int x;
  x = 1;
  while( x < 10) {
    if (x % 3 == 0) {
      cout << x << " is divisible by 3." << endl;
    }
    x++;
  }


    1	for(int x = 1; x < 10; x++) {
    2	    if (x % 3 == 0) {
    3	      cout << x << " is divisible by 3." << endl;
    4	    }
    5	    x++;
    6	}


    1	for(int x = 1; x < 10; x++) {
    2	    x++;
    3	    if (x % 3 == 0) {
    4	      cout << x << " is divisible by 3." << endl;
    5	    }
    6	}


    1	for(int x = 1; x < 10; x++) {
    2	    if (x % 3 == 0) {
    3	      cout << x << " is divisible by 3." << endl;
    4	    }
    5	}


    1	for( int x;  x < 10; x++) {
    2	    if (x % 3 == 0) {
    3	      cout << x << " is divisible by 3." << endl;
    4	    }
    5	}

next prev start

Which while loop below is equivalent to this for loop:


int n;
for(n = 10; n > 0; n--) {
  p *= n;
}


int n;
n = 10;
while( n > 0 ) {
  n--;
  p *= n;
}


int n = 10;
while( n > 0 ) {
  n--;
  p *= n;
}


int n;
n = 10;
while( n > 0 ) {
  p *= n;
  n--;
}


int n = 10;
while( n > 0 ) {
  p *= --n;
}

next prev start

What is the output of the following program?


#include <iostream>

int main()
{
  for(int i = 0; i < 5; i++) {
    cout << "A";
  }
  return 0;
}

AAAA
AAAAA
A
A
A
A
A
A
A
A
A

next prev start

What is the output of this program? (Note the 2 slight changes from the program in the previous problem.)
```
#include <iostream>

int main()
{
  for(int i = 1; i < 5; i++) {
    cout << "A" << endl;;
  }
  return 0;
}
```
1. AAAA
2. AAAAA
3. A
  A
  A
  A
4. A
  A
  A
  A
  A
next prev start

Which of the following will print exactly 10 copies of X?


#include <iostream>

int main()
{
  for(int i = 0; i <= 10; i++) {
    cout << "X";
  }
  cout << endl;
  return 0;
}


#include <iostream>

int main()
{
  for(int i = 1; i < 10; i++) {
    cout << "X";
  }
  cout << endl;
  return 0;
}


#include <iostream>

int main()
{
  for(int i = 0; i < 10; i++) {
    cout << "X";
  }
  cout << endl;
  return 0;
}


#include <iostream>

int main()
{
  for(int i = 0; i < 11; i++) {
    cout << "X";
  }
  cout << endl;
  return 0;
}

next prev start

What is output if input is 'Tristram Shandy' (without the quotes)?


    1	#include <iostream>
    2	#include <string>
    3	using namespace std;
    4	
    5	int main()
    6	{
    7	  string name;
    8	  cout << "Enter a name (no spaces): ";
    9	  cin >> name;
   10	  int n = name.length();
   11	
   12	  for(int i = 0; i < n + 2; i++) {
   13	    cout << "*";
   14	  }
   15	
   16	  cout << endl;
   17	  cout << "*" << name << "*" << endl;
   18	
   19	  for(int i = 0; i < n + 2; i++) {
   20	    cout << "*";
   21	  }
   22	  cout << endl;
   23	
   24	  
   25	  return 0;
   26	}


*****************
*Tristram Shandy*
*****************

```
**********
*Tristram*
**********
```


***************
*Tristram Shandy*
***************

```
********
*Tristram*
********
```

next prev start

What does this code do?
```
int sum = 0;
for(int i = 1; i <= 10; i += 2) {
  sum += i;
} 
cout << sum << endl;
```
1. Prints the sum of the 1 + 2 + ... + 10
2. Prints the sum of the 1 + 2 + ... + 5
3. Prints the sum of the 2 + 4 + 6 + ... + 10
4. Prints the sum of the 1 + 3 + 5 ... + 9
next prev start

What is output?


int a = 1;
for( int k = 0; k < 4; k++) {
  a *= 2;
}
cout << a << endl;

next prev start