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In this post, you will find the solution for **Common Child in Java-HackerRank Problem**. We are providing the **correct and tested solutions** of coding problems present on **HackerRank**. If you are not able to solve any problem, then you can take help from our Blog/website.

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**Introduction To Algorithm**

The word **Algorithm** means “a process or set of rules to be followed in calculations or other problem-solving operations”. Therefore Algorithm refers to a set of rules/instructions that step-by-step define how a work is to be executed upon in order to get the expected results.

**Advantages of Algorithms:**

- It is easy to understand.
- Algorithm is a step-wise representation of a solution to a given problem.
- In Algorithm the problem is broken down into smaller pieces or steps hence, it is easier for the programmer to convert it into an actual program.

** Link for the Problem** – Common Child – Hacker Rank Solution

Common Child – Hacker Rank Solution

**Problem:**

A string is said to be a child of a another string if it can be formed by deleting 0 or more characters from the other string. Letters cannot be rearranged. Given two strings of equal length, what’s the longest string that can be constructed such that it is a child of both?

**Example**

These strings have two children with maximum length 3, `ABC`

and `ABD`

. They can be formed by eliminating either the `D`

or `C`

from both strings. Return .

**Function Description**

Complete the *commonChild* function in the editor below.

commonChild has the following parameter(s):

*string s1:*a string*string s2:*another string

**Returns**

*int:*the length of the longest string which is a common child of the input strings

**Input Format**

There are two lines, each with a string, and .

**Constraints**

- where means “the length of “
- All characters are upper case in the range ascii[A-Z].

**Sample Input**

HARRY SALLY

**Sample Output**

2

**Explanation**

The longest string that can be formed by deleting zero or more characters from and is , whose length is 2.

**Sample Input 1**

AA BB

**Sample Output 1**

0

**Explanation 1**

and have no characters in common and hence the output is 0.

**Sample Input 2**

SHINCHAN NOHARAAA

**Sample Output 2**

3

**Explanation 2**

The longest string that can be formed between and while maintaining the order is .

**Sample Input 3**

ABCDEF FBDAMN

**Sample Output 3**

2

**Explanation 3**

is the longest child of the given strings.

`Common Child – Hacker Rank Solution`

import java.util.Scanner; public class CommonChild { static int commonChild(String s1, String s2) { return LCSM4(s1.toCharArray(), s2.toCharArray(), s1.length(), s2.length()); } public static int LCSM4(char[] X, char[] Y, int m, int n) { int memo[] = new int[n + 1]; for (int i = 1; i <= m; i++) { int prev = 0; for (int j = 1; j <= n; j++) { int temp = memo[j]; if (X[i - 1] == Y[j - 1]) { memo[j] = prev + 1; } else { memo[j] = Math.max(memo[j], memo[j - 1]); } prev = temp; } } return memo[n]; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); String s1 = sc.next(); String s2 = sc.next(); int result = commonChild(s1, s2); System.out.println(result); sc.close(); } }