public int GCD(int a, int b) {
if (b==0) return a;
return GCD(b,a%b);
}
Power(Base, N) – 1
Check if number is divisible from 2 till root(N)
public class CountRepeatedWords {
public static void main(String[] args) {
countRepeatedWords("Note that the order of what you get out of keySet is arbitrary. If you need the words to be sorted by when they first appear in your input String, you should use a LinkedHashMap instead.");
}
public static void countRepeatedWords(String wordToFind) {
String[] words = wordToFind.split(" ");
HashMap<String, Integer> wordMap = new LinkedHashMap<String, Integer>();
for (String word : words) {
wordMap.put(word,
(wordMap.get(word) == null ? 1 : (wordMap.get(word) + 1)));
}
System.out.println(wordMap);
}
}
void markMultiples(bool arr[], int a, int n)
{
int i = 2, num;
while ( (num = i*a) <= n )
{
arr[ num-1 ] = 1;
++i;
}
}
void SieveOfEratosthenes(int n)
{
if (n >= 2)
{
// Create an array of size n and initialize all elements as 0
bool arr[n];
memset(arr, 0, sizeof(arr));
/* Following property is maintained in the below for loop
arr[i] == 0 means i + 1 is prime
arr[i] == 1 means i + 1 is not prime */
for (int i=1; i<n; ++i)
{
if ( arr[i] == 0 )
{
//(i+1) is prime, print it and mark its multiples
printf("%d ", i+1);
markMultiples(arr, i+1, n);
}
}
}
}
CODE
void CalculateOddMagicSquare()
{
n=5;
int matrix[5][5];
int nsqr = n * n;
int i=0, j=n/2; // start position
for (int k=1; k<=nsqr; ++k)
{
matrix[i][j] = k;
i--;
j++;
if (k%n == 0)
{
i += 2;
--j;
}
else
{
if (j==n)
j -= n;
else if (i<0)
i += n;
}
}
int f(int n)
{
int count = 0;
int a; // The current digit a_j
int p = 1; // The current value of 9^j
while (n > 0) {
a = n % 10;
if (a == 3) {
count = 0;
}
if (a <= 3) {
count += a * p;
} else {
count += (a-1) * p;
}
n /= 10;
p *= 9;
}
return count;
}
<!DOCTYPE html>
<html>
<head>
<script>
function loadXMLDoc()
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.open("GET","ajax_info.txt",true);
xmlhttp.send();
}
</script>
</head>
<body>
<div id="myDiv"><h2>Let AJAX change this text</h2></div>
<button type="button" onclick="loadXMLDoc()">Change Content</button>
</body>
</html>
double sqaure_root_of(double value)
{
double lo = 1.0;
double hi = value;
while( hi - lo > 0.00001)
{
double mid = lo + (hi - lo) / 2 ;
if( mid * mid - value > 0.00001)
{
hi = mid;
}
else {
lo = mid;
}
}
return lo;
}
OR
float squareRoot(float n)
{
float x = n;
float y = 1;
float e = 0.000001; /* e decides the accuracy level*/
while(x - y > e)
{
x = (x + y)/2;
y = n/x;
}
return x;
}
Recursion
Node MergeLists(Node list1, Node list2) {
if (list1 == null) return list2;
if (list2 == null) return list1;
if (list1.data < list2.data) {
list1.next = MergeLists(list1.next, list2);
return list1;
} else {
list2.next = MergeLists(list2.next, list1);
return list2;
}
}
Without Recursion
Node MergeLists(Node list1, Node list2) {
if (list1 == null) return list2;
if (list2 == null) return list1;
Node head;
if (list1.data < list2.data) {
head = list1;
} else {
head = list2;
list2 = list1;
list1 = head;
}
while(list1.next != null && list2 != null) {
if (list1.next.data <= list2.data) {
list1 = list1.next;
} else {
Node tmp = list1.next;
list1.next = list2;
list2 = tmp;
}
}
if (list1.next == null) list1.next = list2;
return head;
}
Software development life cycle model phases:
SDLC models:
First Process Model. Each phase must be completed before proceeding to the next phase without any overlapping in the phases.
Some situations where it is most appropriate:
Disadvantage
Whole requirement is divided into various builds. During each iteration, the development module goes through the requirements, design, implementation and testing phases. Each subsequent release of the module adds function to the previous release.
Some situations where it is most appropriate:
Disadvantage
Combination of iterative development process model and sequential linear development model i.e. waterfall model with very high emphasis on risk analysis.
The spiral model has four phases.
Uses of Spiral model:
Disadvantage
Complex management as there is a risk of running the spiral in indefinite loop. Not suitable for small or low risk projects as its expensive.
Extension of the waterfall model and is based on association of a testing phase for each corresponding development stage. There are Verification phases on one side and Validation phases on the other side with Coding phase in between.
Verification phases are:
Validation phases in V-Model:
Uses:
Disadvantage
Not a good model for long and complex and object-oriented projects. No working software is produced until late during the life cycle.
Focusing all the possible resources in software development and coding, with very little or no planning. Ideal for small projects
Advantages
Disadvantages
Breaks the product into small incremental builds which are provided in iterations. Each iteration lasts about 1-3 weeks and involves cross functional teams working simultaneously on various areas like planning, requirements analysis, design, coding, unit testing and acceptance testing.
Iterative approach is taken and working software build is delivered after each iteration. Each build is incremental in terms of features; the final build holds all the features required by the customer.
The most popular agile methods include Rational Unified Process (1994), Scrum (1995), Extreme Programming (1996), Adaptive Software Development and Dynamic Systems Development Method (DSDM) (1995).
Disadvantages
Different types of software prototypes:
Container class
Stores a collection of other objects and provide sequential or direct access to them. The string class is a container that holds chars. All container classes access the contained elements safely and efficiently by using iterators. Container class is a class that hold group of same or mixed objects in memory.
Containers of pointers provide containers to hold the objects that are heap-allocated in manner that is exception-safe and with minimum overhead.
Types
Functions that:
Example:
Creating containers: vector<int> numbers(7);
Extending a container: vector<int> v; // creates an empty vector
v.push_back(3);
v.push_back(8);
Accessing elements of a container: v[1]=3;
v[2]=5;
v[3]=v[1]+v[2];
find - looks for a value
vector<int>::iterator it;
...
it = find (v.begin(), v.end(), 30);
if (it == v.end())
cout << "30 not found " << endl;
else
cout << "30 is in v " << endl;
count
vector<int> v;
cout << "30 is in v " << count(v.begin(), v.end(), 30) << " times" << endl;
for_each
void square(int n) {
cout << n*n << endl;
}
vector<int> v;
// print the square of all the values in v
for_each(v.begin(), v.end(), square);
transform
int square(int n) {
return n*n;
}
vector<int> v;
// replace each value in v by its square
transform(v.begin(), v.end(), square);
Replace
replace(v.begin(), v.end(), 7,3);
fill
fill(v,9);
copy
vector<int> v(10);
for (int i=0;i<v.size();i++)
v[i]=i;
list<int> l(10);
copy(v.begin(), v.end(),l.begin());
remove
it=remove (v.begin(), v.end(), 7);
min_element
it=min_element(v.begin(), v.end());
Adapter class
Provides an empty implementation of all methods in an event listener interface i.e this class itself write definition for methods which are present in particular event listener interface. However these definitions does not affect program flow or meaning at all.
useful when you want to receive and process only some of the events that are handled by a particular event listener interface.
Suppose you want to use MouseClicked Event or method from MouseListener, if you do not use adapter class then unnecessarily you have to define all other methods from MouseListener such as MouseReleased, MousePressed etc.
But If you use adapter class then you can only define MouseClicked method and don’t worry about other method definition because class provides an empty implementation of all methods in an event listener interface.
Example:
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
/*
<applet code="MainClass" height="800" width = "500">
</applet>
*/
public class MainClass extends Applet
{
public void init()
{
addMouseListener(new AdapterTest(this));
}
}
// AdapterTest Created
class AdapterTest extends MouseAdapter
{
MainClass MainClassObj;
public AdapterTest(MainClass MainClassObj)
{
this.MainClassObj=MainClassObj;
}
public void mouseClicked(MouseEvent me)
{
MainClassObj.showStatus("Mouse Has Been Clicked ");
}
}
Memory space for a program has two parts:
A data segment is a portion of virtual address space of a program, which contains the global variables and static variables that are initialized by the programmer. The size of this segment is determined by the values placed there by the programmer before the program was compiled or assembled, and does not change at run-time. The data segment is read-write, since the values of the variables can be altered at run-time.
Example – Stack, Heap, uninitialized and initialized data
It is one of the sections of a program in an object file or in memory, which contains executable instructions. It has a fixed size and is usually read-only. If the text section is not read-only, then the particular architecture allows self-modifying code.
Example – main()
Finalize method
Before an object is garbage collected, the runtime system calls its finalize() method. The intent is for finalize() to release system resources such as open files or open sockets before object gets collected.
By using finalization, you can define specific actions that will occur when an object is just about to be reclaimed by the garbage collector. It is not called when an object goes out-of-scope.
To add a finalizer to a class, you simply define the finalize() method. The java run time calls that method whenever it is about to recycle an object of that class. Inside the finalize() method you will specify those actions that must be performed before an object is destroyed.
protected void finalize() // protected is used to prevent access by code defined outside its class.
{
// finalization code here
}
Learn By Coding 