• Space complexity is a measure of how efficient your code is in terms of memory used.

• Memory management is the process of controlling and coordinating computer memory, assigning portions called blocks to various running programs to optimize overall system performance.
• Memory management resides in hardware, in the OS (operating system), and in applications.
• In hardware, memory management involves components that physically store data, such as RAM chips, memory caches,etc.,.
• In the OS, memory management involves the allocation (and constant reallocation) of specific memory blocks to individual programs as user demands change.
• At the application level, memory management ensures the availability of adequate memory for the objects and data structures of each running program at all times.Application memory management combines two related tasks, known as allocation and recycling.
  • Allocation : When the program requests a block of memory, a part of the memory manager called the allocator assigns that block to the program.
  • Recycling : When a program no longer needs the data in previously allocated memory blocks, those blocks become available for reassignment. This task can be done manually (by the programmer) or automatically (by the memory manager).

• As processes are loaded and removed from memory, the free memory space has broken into small pieces.
• That processes cannot be allocated to memory blocks considering their small size and memory blocks remains unused.
• This problem is known as Fragmentation.There are two types of fragmentation,
  • Internal fragmentation
  • External fragmentation

• Memory block assigned to process is lager. Memory is left unused in some portion as it cannot be used by another process.

• Total memory space is enough to satisfy a request or to reside a process in it, but it is not contiguous, so it cannot be used.

• One of the simplest Sorting techniques is a linear sort.
• Linear sort is the selection of an element and keeping it in sorted order.
• In linear sort, the strategy is to find the smallest number in the array and exchange it with the value in first position of array.
• Now, find the second smallest element in the remainder of array and exchange it with a value in the second position, carry on till you have reached the end of array.
• Now all the elements have been sorted in ascending order.

• The same URL can be encoded multiple times, we need to decode it until the URL cannnot be decoded further. For example, “video%252Fmp4” is the result of two encodings. Upon decoding it once, we get “video%2Fmp4”. Now the URL needs to be further decoded so that we get “video/mp4”, which is the result.
• We use the decode method of a predefined Java class named URLDecoder.
• The decode method of URLDecoder takes two arguments:
  • The first argument defines the URL to be decoded.
  • The second argument defines the decoding scheme to be used.
• After decoding, the resulting decoded URL is returned.
• We create two variables: prevURL, which is empty, and decodeURL, which contains the URL to be decoded.
• We create an iteration that runs until prevURL!=decodeURL
• Now we update prevURL to decodeURL and update decodeURL with the decoded value of the URL passed.
• As you can see, prevURL!=decodeURL, so we run it again and again.
• Now, prevURL=decodeURL, so the decoded URL is returned.

Sample Code

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
 
public class DecodeURLExample {
    public static void main(String a[]){
        try {
            System.out.println(URLDecoder.decode("special+chars%3A+%26%25*+", "UTF-8"));
        } catch (UnsupportedEncodingException ex) {
            ex.printStackTrace();
        }
    }
}

special chars: &%* 

• A palindrome is a word, phrase, number, or other sequence of characters which reads the same backward as forward, example as madam.
• Write a java program to find the longest palindrome present in a given string.

• The string can be of odd or even length and hence the findLongestPalindromeWithSpecifiedParameter() is called twice for each string.
• In the method, findLongestPalindromeWithSpecifiedParameter() left will decrement and move towards the start of the string until it reaches start and then right will increment and move towards the end of the string until it reaches the end.
• And any left and right reach destination (i.e. start and end respectively)at any point then the method will return.