Winter 2020

PIC 10A: Introduction to Programming

Discussion Section 3A

Wonjun Lee

Week10

Tuesday and Thursday

Many problems related to vector

Exercise P6.5.

Check the textbook to see the problem

Solution
#include < iostream >
#include < cmath > // We use fmax function
#include < vector > // We use vector function

using namespace std;

vector< int > merge(vector< int >& a, vector< int >& b)
{
	vector< int > c;

	int larget_num = fmax(a.size(), b.size());

	for(int i=0 ; i < larget_num; ++i)
	{
		if(i < a.size())
		{
			c.push_back(a[i]);
		}
		if(i < b.size())
		{
			c.push_back(b[i]);
		}
	}
	return c;
}

int main()
{
	vector< int > a = {1,1,1,1};
	vector< int > b = {3,3,3,3,3,3};

	vector< int > c = merge(a,b);

	for(int i=0;i < c.size(); ++i)
	{
		cout << c[i] << endl;
	}
}
Exercise P6.7.

Check the textbook to see the problem

Solution
#include < iostream >
#include < vector > // We use vector function

using namespace std;

bool equals(vector< int >& a, vector< int >& b)
{
	if(a.size() != b.size())
	{
		return false;
	}

	for(int i=0; i < a.size(); ++i)
	{
		if(a[i] != b[i])
		{
			return false;
		}
	}
	return true;
}

int main()
{
	vector< int > a = {1,1,1,1};
	vector< int > b = {3,3,3,3,3,3};

	bool same = equal(a,b);

	cout << same << endl; // will return false
}
Exercise P6.9.

Check the textbook to see the problem

Solution
#include < iostream >
#include < vector > // We use vector function

using namespace std;

bool equals(vector< int >& a, vector< int >& b)
{
	if(a.size() != b.size())
	{
		return false;
	}

	for(int i=0; i < a.size(); ++i)
	{
		if(a[i] != b[i])
		{
			return false;
		}
	}
	return true;
}

void permutation(vector< int >& a) // Here you need to put & because you need to modify a vector at the end
{
	vector< int > c; // initialize a new vector c

	for(int i=0; i < a.size(); ++i)
	{
		c.push_back(a[(i+3) % a.size()]);
	}
	a = c;
}

bool same_elements(vector< int > a, vector< int > b)
{
	// check if two vectors have the same number of items
	if(a.size() != b.size())
	{
		return false;
	}

	for(int i=0; i < a.size(); ++i)
	{
		permutation(b);
		if(equal(a,b) == true)
		{
			return true;
		}
	}
	return false;
}

int main()
{
	vector< int > a = {1,2,3,4};
	vector< int > b = {4,1,2,3};

	bool same = same_elements(a,b);

	cout << same << endl; // will return true
}
Exercise P6.10.

Check the textbook to see the problem

Solution
#include < iostream >
#include < vector > // We use vectors

using namespace std;

// This function will check if an integer n is in a vector a
// Suppose a = {1,2,3} and n = 2. Then check(n,a) will return true.
bool check(int n, vector< int > a)
{
	for(int i=0; i < a.size(); ++i)
	{
		// if one of items in a is equal to n then return true.
		if(a[i] == n)
		{
			return true;
		}
	}

	// if none of them equal to n then return false.
	return false;
}

void remove_duplicates(vector< int >& a)
{
	// initialzie a new vector c
	vector< int > c;

	for(int i=0; i < a.size(); ++i)
	{
		if(check(a[i], c) == false) // check if an integer a[i] is in a vector c. If it doesn't then push back to c.
		{
			c.push_back(a[i]);
		}
	}
	a = c;
}

int main()
{
	vector< int > a = {1,1,1,5,5,5,2,2,6,6,1,2,6};

	remove_duplicates(a);

	// This will print out 1, 5, 2, 6,
	for(int i=0; i < a.size(); ++i)
	{
		cout << a[i] << ", ";
	}
	cout << endl;
}