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finished implementation #3

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6 changes: 6 additions & 0 deletions .idea/vcs.xml
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40 changes: 40 additions & 0 deletions src/Main.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,49 @@ public static void main(String[] args) {

Deque<String> d1 = new ResizingArrayDeque<>();
// some test code here
d1.addFirst("Hi");
System.out.println(d1);
d1.removeFirst();
System.out.println(d1);
d1.addLast("hi");
System.out.println(d1);
d1.removeLast();
System.out.println(d1);
d1.addFirst("no");
d1.addFirst("yes");
d1.addLast("how");
System.out.println(d1);
d1.removeFirst();
System.out.println(d1);
d1.removeLast();
System.out.println(d1);

//
System.out.println("END OF ARRAY TESTS");

Deque<String> d2 = new SinglyLinkedDeque<>();
// some test code here
d2.addFirst("Hi");
System.out.println(d2);
d2.removeFirst();
System.out.println(d2);
d2.addLast("hi");
System.out.println(d2);
d2.removeLast();
System.out.println(d2);
d2.addFirst("no");
d2.addFirst("yes");
d2.addLast("how");
System.out.println(d2);
d2.removeFirst();
System.out.println(d2);
d2.removeLast();
System.out.println(d2);
d2.addLast("know");
d2.addLast("not");
d2.addLast("where");
d2.removeLast();
System.out.println(d2);

}
}
94 changes: 71 additions & 23 deletions src/ResizingArrayDeque.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,21 @@ public int size() {
@Override
public void addFirst(ItemType item) {
// consider the case of adding to an empty list
// consider the case of adding to a non-empty list
if (size == 0) {
data[0] = item;
size++;
}else { // consider the case of adding to a non empty list
// check if the array needs to be resized
checkSize();
// loop from the back of the array to the front
for(int i=size-1; i>=0; i--) {
// set the next index to the current index
data[i+1] = data[i];
}
// set the first index to the item
data[0] = item;
size++;
}

// There is a private helper method checkSize() defined below to check/resize
// that you can call as needed to check if the array is full and resize it.
Expand All @@ -46,7 +60,16 @@ public void addFirst(ItemType item) {
@Override
public void addLast(ItemType item) {
// consider the case of adding to an empty list
// consider the case of adding to a non-empty list
if (size == 0) {
data[0] = item;
size++;
} else { // consider the case of adding to a non-empty list
// check for a resize
checkSize();
// set the last (empty) index to the item
data[size] = item;
size++;
}

// There is a private helper method checkSize() defined below to check/resize
// that you can call as needed to check if the array is full and resize it.
Expand All @@ -60,17 +83,27 @@ public void addLast(ItemType item) {
@Override
public ItemType removeFirst() {
// check if empty
// if empty: do nothing and return null

// if there's only one item: is this a special case?

// if not empty:
// 0. figure out a way to access the item in the front
// 1. make a variable to save a copy of the item at the front
// 2. remove the item at the front
// 3. return the variable that has the saved copy of the item at the front

return null;
if (size == 0) {
// if empty: do nothing and return null
return null;
} else if (size == 1) {// if there's only one item: is this a special case?
ItemType removed = data[0];
data[0] = null;
size--;
return removed;
} else {// if not empty:
// 0. figure out a way to access the item in the front
ItemType removed = data[0];
// 1. make a variable to save a copy of the item at the front
// 2. remove the item at the front
for (int i=0; i<size; i++) {
//shift all items in the array back one index
data[i] = data[i+1];
}
size--;
// 3. return the variable that has the saved copy of the item at the front
return removed;
}
}

/**
Expand All @@ -82,16 +115,23 @@ public ItemType removeFirst() {
public ItemType removeLast() {
// check if empty
// if empty: do nothing and return null

// if there is only one item: is this a special case?

// if not empty, has more than one item:
// 0. figure out a way to access the item in the back
// 1. make a variable to save a copy of the item at the back
// 2. remove the item at the back
// 3. return the variable that has the saved copy of the item at the back

return null;
if (size == 0) {
return null;
} else if (size == 1) {// if there's only one item: is this a special case?
ItemType removed = data[0];
data[0] = null;
size--;
return removed;
} else { // if not empty, has more than one item:
// 0. figure out a way to access the item in the back
// 1. make a variable to save a copy of the item at the back
ItemType removed = data[size-1];
// 2. remove the item at the back
data[size-1] = null;
size--;
// 3. return the variable that has the saved copy of the item at the back
return removed;
}
}

// helper method to check to see if the size has reached the capacity
Expand All @@ -116,4 +156,12 @@ private void checkSize() {
temp = null;
} // end of if (need to resize)
}

public String toString() {
String result = "";
for (int i=0; i<size; i++) {
result += data[i] + " ";
}
return result;
}
}
110 changes: 89 additions & 21 deletions src/SinglyLinkedDeque.java
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,23 @@ public int size() {
@Override
public void addFirst(ItemType item) {
// consider the case of adding to an empty list
// consider the case of adding to a non-empty list
if (size == 0) {
Node newNode = new Node();
newNode.data = item;
newNode.next = null;
head = newNode;
size++;
} else {// consider the case of adding to a non-empty list
// create a new node
Node newNode = new Node();
// give the newNode the item as its data
newNode.data = item;
// set newNode's next equal to the head
newNode.next = head;
// set the head equal to the newNode
head = newNode;
size++;
}
}

/**
Expand All @@ -46,7 +62,28 @@ public void addFirst(ItemType item) {
@Override
public void addLast(ItemType item) {
// consider the case of adding to an empty list
// consider the case of adding to a non-empty list
if (size == 0) {
Node newNode = new Node();
newNode.data = item;
newNode.next = null;
head = newNode;
size++;
} else {// consider the case of adding to a non-empty list
// create a new node with the item as its data
Node newNode = new Node();
newNode.data = item;
newNode.next = null;
// loop until the end of the list, keeping track of the current node
Node current = head;
while (current.next != null) {
// move current to the next node
current = current.next;
}
// at the end of the list....
// set the next node equal to the new node
current.next = newNode;
size++;
}
}

/**
Expand All @@ -58,16 +95,22 @@ public void addLast(ItemType item) {
public ItemType removeFirst() {
// check if empty
// if empty: do nothing and return null

// if there's only one item: is this a special case?

// if not empty:
// 0. figure out a way to access the item in the front
// 1. make a variable to save a copy of the item at the front
// 2. remove the item at the front
// 3. return the variable that has the saved copy of the item at the front

return null;
if (size == 0) {
return null;
} else if (size == 1) {// if there's only one item: is this a special case?
ItemType removed = head.data;
head = null;
size--;
return removed;
} else { // if not empty:
// 1. make a variable to save a copy of the item at the front
ItemType removed = head.data;
// 2. remove the item at the front
head = head.next;
// 3. return the variable that has the saved copy of the item at the front
size--;
return removed;
}
}

/**
Expand All @@ -79,15 +122,40 @@ public ItemType removeFirst() {
public ItemType removeLast() {
// check if empty
// if empty: do nothing and return null
if (size == 0) {
return null;
} else if (size == 1) {// if there's only one item: is this a special case?
ItemType removed = head.data;
head = null;
size--;
return removed;
} else { // if not empty:
// 0. figure out a way to access the item in the back
// create nodes to keep track of current and previous
Node previous = null;
Node current = head;
// loop to the end of the list, keeping track of current
while (current.next != null) {
previous = current;
current = current.next;
}
// 1. make a variable to save a copy of the item at the back
ItemType removed = current.data;
// 2. remove the item at the back
previous.next = null;
size--;
// 3. return the variable that has the saved copy of the item at the back
return removed;
}
}

// if there is only one item: is this a special case?

// if not empty, has more than one item:
// 0. figure out a way to access the item in the back
// 1. make a variable to save a copy of the item at the back
// 2. remove the item at the back
// 3. return the variable that has the saved copy of the item at the back

return null;
public String toString() {
String result = "";
Node current = head;
while (current != null) {
result += current.data + " ";
current = current.next;
}
return result;
}
}