COMP 1672 Sections 1 & 2
Homework #3, solutions

1. What is the output from the following program?  Give an explanation
of what is happening line-by-line

output is:
10
100
2000
3000

int main()
{
	int nums[5];    // declare a 5-member integer array called nums
	nums[0] = 10;   // initialize the
	nums[1] = 100;  // values of the
	nums[2] = 1000; // array
	nums[3] = 2000;
	nums[4] = 3000;

	bar(nums);      // call the function called bar, pass it the array
	return 0;       // exit program, successfully
}

void bar(int *input)
{
	cout << *input << endl;  // input points to the first array element
                                 // (which is element number 0)
                                 // output its contents, which is the number 10
	input++;                 // update the pointer to point to the 2nd
                                 // array element (which is element number 1)
	cout << *input << endl;  // output its contents, which is the number 100
	input+=2;                // increment the pointer by 2, so it now points
                                 // to the 4th array element (element 3)
	cout << *input << endl;  // output its contents, which is 2000
	input++;                 // increment the pointer by 1, it points
                                 // to the 5th array element (element 4)
	cout << *input << endl;  // output its contents, which is 3000.
}

2. 
    After the initializations, the memory map looks like this:
    0x100:      6     /* note: the integer x is stored here
    0x104:      7     /* note: the integer y is stored here
    0x108:  0x100     /* note: the integer pointer p is stored here
    0x10C:  0x104     /* note: the integer pointer q is stored here

    cout << x << " " << y << " " << p << " " << q << " "
             << *p << " " << *q << endl;
    The above line outputs 6 7 0x100 0x104 6 7

    *p = 7;   After this line is executed, here's the new memory map:
    0x100:      7     /* note: the integer x is stored here
    0x104:      7     /* note: the integer y is stored here
    0x108:  0x100     /* note: the integer pointer p is stored here
    0x10C:  0x104     /* note: the integer pointer q is stored here
 
    cout << x << " " << y << " " << p << " " << q << " "
             << *p << " " << *q << endl;
    The above line now outputs 7 7 0x100 0x104 7 7

    if(p == q)  // (No, p and q point to different places in memory!)
    {
	cout << "Equal" << endl;   // this does NOT get output
    }

    p = q;   // Now p takes the value 0x104
    y = 10;  // The value of y has been changed
    Here's the new memory map:
    0x100:      7     /* note: the integer x is stored here
    0x104:     10     /* note: the integer y is stored here
    0x108:  0x104     /* note: the integer pointer p is stored here
    0x10C:  0x104     /* note: the integer pointer q is stored here
    cout << x << " " << y << " " << p << " " << q << " "
             << *p << " " << *q << endl;
    The above line now outputs 7 10 0x104 0x104 7 10

3. Write a program using vectors that does the following (in order).

#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector <int> myvector;
    vector <int>::iterator myiterator;
    
    myvector.push_back(3);
    myvector.push_back(6);
    myvector.push_back(8);
    myvector.pop_back();
    cout << "The size of the vector is " << myvector.size() << endl;
    myvector.push_back(5);
    for (myiterator=myvector.begin(); myiterator!=myvector.end();myiterator++)
        cout << *myiterator << endl;
    myvector.clear();
    return 0;
}