From dff8907818ff7ce00addfce76fbeca225da01741 Mon Sep 17 00:00:00 2001
From: Revathi Mukkamala <rmukkamala@twilio.com>
Date: Sat, 18 Jan 2025 17:37:48 -0800
Subject: [PATCH] Precourse 1
---
Exercise_1.java | 36 +++++++++++++++++++++++++++++-------
Exercise_2.java | 47 ++++++++++++++++++++++++++++++++++++++++-------
Exercise_3.java | 39 ++++++++++++++++++++++++++++-----------
3 files changed, 97 insertions(+), 25 deletions(-)
diff --git a/Exercise_1.java b/Exercise_1.java
index 314a3cb45..cb9fcc8e1 100644
--- a/Exercise_1.java
+++ b/Exercise_1.java
@@ -1,4 +1,6 @@
-class Stack {
+import java.util.Arrays;
+
+class Stack {
//Please read sample.java file before starting.
//Kindly include Time and Space complexity at top of each file
static final int MAX = 1000;
@@ -6,31 +8,51 @@ class Stack {
int a[] = new int[MAX]; // Maximum size of Stack
boolean isEmpty()
- {
- //Write your code here
+ {
+ return 0 == top;
}
Stack()
{
- //Initialize your constructor
+ //Initialize your constructor
+ top = 0;
}
boolean push(int x)
{
//Check for stack Overflow
//Write your code here
+ if( top+1 > MAX) {
+ return false;
+ }
+ a[top] = x;
+ top = top + 1;
+ return true;
}
int pop()
{
//If empty return 0 and print " Stack Underflow"
//Write your code here
+ if(top == 0) {
+ return 0;
+ }
+ int new_array[] = new int[MAX];
+ int value = a[top-1];
+ for(int i=0; i<top-1; i++) {
+ new_array[i] = a[i];
+ }
+ a=new_array;
+ top = top -1;
+ return value;
}
int peek()
{
//Write your code here
- }
+ return a[top- 1];
+ }
+
}
// Driver code
@@ -40,7 +62,7 @@ public static void main(String args[])
Stack s = new Stack();
s.push(10);
s.push(20);
- s.push(30);
- System.out.println(s.pop() + " Popped from stack");
+ s.push(30);
+ System.out.println(s.pop() + " Popped from stack");
}
}
diff --git a/Exercise_2.java b/Exercise_2.java
index 5a9c4868c..9e6e1b593 100644
--- a/Exercise_2.java
+++ b/Exercise_2.java
@@ -1,4 +1,4 @@
-public class StackAsLinkedList {
+public class StackAsLinkedList {
StackNode root;
@@ -8,38 +8,71 @@ static class StackNode {
StackNode(int data)
{
- //Constructor here
+ //Constructor here
+ this.data = data;
}
}
public boolean isEmpty()
{
- //Write your code here for the condition if stack is empty.
+ //Write your code here for the condition if stack is empty.
+ return null == root;
}
public void push(int data)
- {
- //Write code to push data to the stack.
+ {
+ //Write code to push data to the stack.
+ StackNode new_node = new StackNode(data);
+ if(null == root){
+ root = new_node;
+ return;
+ }
+ StackNode temp = root;
+ while(temp.next != null) {
+ temp = temp.next;
+ }
+ temp.next = new_node;
}
public int pop()
{
//If Stack Empty Return 0 and print "Stack Underflow"
//Write code to pop the topmost element of stack.
- //Also return the popped element
+ //Also return the popped element
+ if(isEmpty()){
+ System.out.println("Stack Underflow");
+ return 0;
+ }
+ StackNode temp = root;
+ while(temp.next != null && temp.next.next != null) {
+ temp = temp.next;
+ }
+ StackNode pop_node = temp.next;
+ temp.next = null;
+ return pop_node.data;
}
public int peek()
{
//Write code to just return the topmost element without removing it.
+ if(isEmpty()){
+ System.out.println("Stack Underflow");
+ return 0;
+ }
+ StackNode temp = root;
+ while(temp.next != null) {
+ temp = temp.next;
+ }
+ StackNode pop_node = temp;
+ return pop_node.data;
}
//Driver code
public static void main(String[] args)
{
- StackAsLinkedList sll = new StackAsLinkedList();
+ StackAsLinkedList sll = new StackAsLinkedList();
sll.push(10);
sll.push(20);
diff --git a/Exercise_3.java b/Exercise_3.java
index fb66d329d..b504d0dd7 100644
--- a/Exercise_3.java
+++ b/Exercise_3.java
@@ -2,7 +2,7 @@
// Java program to implement
// a Singly Linked List
-public class LinkedList {
+public class LinkedList {
Node head; // head of list
@@ -17,41 +17,58 @@ static class Node {
// Constructor
Node(int d)
{
- //Write your code here
+ //Write your code here
+ this.data = d;
}
}
// Method to insert a new node
- public static LinkedList insert(LinkedList list, int data)
+ public static LinkedList insert(LinkedList list, int data)
{
- // Create a new node with given data
+ // Create a new node with given data
+ Node new_node = new Node(data);
// If the Linked List is empty,
- // then make the new node as head
+ // then make the new node as head
// Else traverse till the last node
// and insert the new_node there
// Insert the new_node at last node
- // Return the list by head
-
+ // Return the list by head
+ if (null == list.head){
+ list.head = new_node;
+ return list;
+ }
+
+ Node temp = list.head;
+ while(temp.next != null) {
+ temp = temp.next;
+ }
+ temp.next = new_node;
+ return list;
}
// Method to print the LinkedList.
- public static void printList(LinkedList list)
+ public static void printList(LinkedList list)
{
// Traverse through the LinkedList
// Print the data at current node
- // Go to next node
+ // Go to next node
+ Node temp = list.head;
+ while(temp != null){
+ System.out.println(temp.data);
+ temp = temp.next;
+ }
}
// Driver code
public static void main(String[] args)
{
/* Start with the empty list. */
- LinkedList list = new LinkedList();
+ LinkedList list = new LinkedList();
//
// ******INSERTION******
@@ -67,4 +84,4 @@ public static void main(String[] args)
// Print the LinkedList
printList(list);
}
-}
\ No newline at end of file
+}