DEV Community: Pankaj Singh

React Logo Using Only 2 Div In Pure CSS

Pankaj Singh — Fri, 04 Feb 2022 13:55:00 +0000

Google Logo Using Single Div In Pure CSS

Pankaj Singh — Fri, 04 Feb 2022 13:52:58 +0000

Lightning Effect Using CSS Animation

Pankaj Singh — Fri, 04 Feb 2022 13:51:06 +0000

🎯 Objects in JavaScripts

Pankaj Singh — Sat, 22 Jan 2022 14:38:21 +0000

In simple words objects is the collection of name-value pairs. Objects is JavaScript are same as dictionaries in Python , hashtable in c and c++ and hashmap in Java.
The "name" part is a JavaScript string, while the value can be any JavaScript value

There are two ways of creating the object
1 - using object literal (more convenient)
2 - using new keyword
👇

A simple example

🎯 10 most useful string methods in Java

Pankaj Singh — Wed, 19 Jan 2022 17:55:20 +0000

Introduction on Strings
String is an object that represents sequence of char values. Strings are immutable in Java.There are two ways to create string in Java
1 - By String literal
2 - By new keyword

📌 Note: String literal create no new object if it exists already in the string constant pool (SCP) which is a special place for all strings in heap memory. Create string of same object using new keyword.This will create new object outside the string pool if it already exist in it

1 - indexOf() used to find characters and substrings in a string. It returns the index of first occurrence from left of the passed string or character
syntax - public int indexOf(String str, int fromIndex)
str - substring to be search
fromIndex - search begin from this index

2 - toCharArray() used to form a character array of a string
syntax - public char[] toCharArray()

▶️Example : check if string is palindrome of not

3 - charAt() Used to find the character at particular index
syntax - public char charAt(int index)

▶️ Example : count no. of spaces in the string

4 - concat() Used to concatenate two strings
syntax - public String concat(String str)

▶️ Example : concatenate last name and firstname

5 - replace() Used for replacing characters and substrings in a string
syntax - public String replace(char oldChar, char newChar)

▶️ Example : remove all white spaces from the string

6 - substring() Used to extract a portion of a string from original string
syntax - public String substring(int beginIndex, int endIndex)

▶️Example : print first 3 character of a string

7 - split() Used to breaks a given string around matches of the given regular expression.After splitting against the given regular expression, this method returns a char array
syntax - public String[] split(String regex, int limit)
limit : number of strings return after split

8 - compareTo() It compares the given string with the current string lexicographically. It returns a positive number, negative number, or 0
if s1 > s2, returns +ve number
if s1 < s2, returns -ve number
if s1 == s2, returns 0
syntax : public int compareTo(String anotherString)

9 - strip() To eliminate all trailing and leading whitespaces from the given string
syntax - public String strip()
▶️ Example

10 - valueOf() Used to return string representation of passed argument
syntax - public static String valueOf(char[] data)
Note : valueOf() has many overloaded variants that aid in the conversion of almost any primitive form to string

🎯 Type Coercion in JavaScript

Pankaj Singh — Wed, 19 Jan 2022 10:23:08 +0000

Type Coercion is process of automatic or implicit conversion of value from one data type to another. Conversion from Number to String , String to Number, Boolean to Number and so on. Type coercion occurs when different types of operators are applied to the values

📌 Number to String : Anything added to string first JavaScript convert it into string and then concatenates both the strings.
Note : It occur only with "+" operator

📌 String to Number : when operation like subtraction( - ), multiplication( * ), division( / ), modulus (%) is performed first JavaScript convert it into number then apply these operations
Note : The string should be a Number

📌 Boolean to Number : when a boolean is added to a Number, boolean value is converted to number as 0 for "false" and 1 for "true"

📌 Equality Operator : The equality ( == ) is used to compare value irrespective of their type. This happen by coercion of Non-Number to Number data type
Note : To avoid type coercion, use the triple-equals operator ( === )

Binary Search Algorithm

Pankaj Singh — Sat, 01 Jan 2022 18:12:40 +0000

What is binary search?
Binary search is one of the searching algorithm used to find element in sorted array in Logarithmic running time complexity

Note: Binary search can only be applied in sorted array

Why binary search is better then linear search
Binary search has O(log(n)) logarithmic time complexity and linear search has O(n) linear time complexity

How Binary Search Work
Binary search use divide and conquer strategy to search element in given array. Binary search divide the searching area into exact half in each pass.

start : it store the value of starting index
end : it stores the value of ending index
mid : it stores the value of middle index

start = 0
end = array_length -1
mid = (start + end)/2 // but that's not good practice
(start + end) can sometime exceed the integer limit

mid = start + (end - start)/2 // this is the correct way

Suppose at first we have an array nums = { 1, 2, 4, 8, 10, 50, 70, 88, 100 } (note here array is sorted) and your target element is 70.
First check if middle element of array is equal to target or not. If it's equal then return middle index or mid. If not then check if target is smaller or bigger then middle element.
If target is smaller then middle element reduce the search space, end = mid -1. Now new search space is (start, mid -1).

If target is bigger the middle element reduce the search space, start = mid +1. Now new search space is (mid+1, end).

Hence, at each pass the search space will reduce into half until start <= end. If start became greater then end, the loop will break

Algorithm
Binary search in Java

import java.util.Arrays;  

public class BinarySearch {
    public static void main(String[] args) {

        int[] nums = { 1, 2, 3, 19, 29, 40, 60, 100 };
        int target = 40;

        System.out.println(Arrays.toString(nums));
        System.out.println(binarySearch(nums, target));
    }

    static int binarySearch(int[] nums, int target) {

        int start = 0;
        int end = nums.length - 1;

        while (start <= end) {

            int mid = start + (end - start) / 2;
            if (nums[mid] == target) {
                return mid;
            } else if (target < nums[mid]) {
                end = mid - 1;
            } else {
                start = mid + 1;
            }

        }

        return -1;
    }
}