updated leetcode solutions

Author: ImAkshayad

README.md

@@ -8,6 +8,7 @@
             - [Time conversion](https://www.hackerrank.com/challenges/time-conversion/problem?isFullScreen=true) | [Solution](hackerrank/algorithms/warmup/time_conversion.py)
         - Implementation
             - [Breaking best and worst records](https://www.hackerrank.com/challenges/breaking-best-and-worst-records/problem) | [Solution](hackerrank/algorithms/implementation/breaking_best_and_worst_records.py)
+    
     - Data structures
         - Linked lists
             [Print the elements of a linked list](https://www.hackerrank.com/challenges/print-the-elements-of-a-linked-list/problem) | [Solution](hackerrank/data_structures/linked_list/print_linked_list_elements.py)
@@ -59,12 +60,17 @@
 
 
 
+    - Java
+        | Problem | Solution |
+        |---|---|
+        |[Java stdin and stdout I](https://www.hackerrank.com/challenges/java-stdin-and-stdout-1)|[Solution](hackerrank\java\introduction\java_stdin_stdout_1.java)|
+        |[Java If Else](https://www.hackerrank.com/challenges/java-if-else)|[Solution](hackerrank\java\introduction\java_if_else.java)|
 - Leetcode
     - Arrays
         | Problem | Python | CPP | Java |
         |---|---|---|---|
         |[Remove duplicates from Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/)|[Solution](leetcode/arrays/python/RemoveDuplicates.py)| | |
-        - [First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/) | [Solution](leetcode/arrays/python/first-unique-character-in-a-string.py)| | |
-        - [Remove Element](https://leetcode.com/problems/remove-element/) | [Solution](leetcode/arrays/python/remove-element.py)| | |
+        |[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/) | [Solution](leetcode/arrays/python/first-unique-character-in-a-string.py)| | |
+        |[Remove Element](https://leetcode.com/problems/remove-element/) | [Solution](leetcode/arrays/python/remove-element.py)| | |
     - Math
-        - [Palindrome Number](https://leetcode.com/problems/palindrome-number/python/description/) | [Solution](leetcode/math/python/palindrome.py)| | |
+        |[Palindrome Number](https://leetcode.com/problems/palindrome-number/python/description/) | [Solution](leetcode/math/python/palindrome.py)| | |

hackerrank/java/introduction/java_if_else.java

@@ -0,0 +1,42 @@
+import java.io.*;
+import java.math.*;
+import java.security.*;
+import java.text.*;
+import java.util.*;
+import java.util.concurrent.*;
+import java.util.regex.*;
+
+public class Solution {
+
+
+
+    private static final Scanner scanner = new Scanner(System.in);
+
+    public static void main(String[] args) {
+        int N = scanner.nextInt();
+        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
+
+        if (N % 2 != 0)
+        {
+            System.out.println("Weird");
+        }
+        else {
+            if (N >= 2 &&  N <= 5)
+            {
+                System.out.println("Not Weird");
+            }
+            else if (N >= 6 &&  N <= 20)
+            {
+                System.out.println("Weird");
+            }
+            else if (N > 20)
+            {
+                System.out.println("Not Weird");
+            }            
+        }
+        
+          
+
+        scanner.close();
+    }
+}

hackerrank/java/introduction/java_stdin_stdout_1.java

@@ -0,0 +1,15 @@
+import java.util.*;
+
+public class Solution {
+
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+        int a = scan.nextInt();
+        int b = scan.nextInt();
+        int c = scan.nextInt();
+
+        System.out.println(a);
+        System.out.println(b);
+        System.out.println(c);
+    }
+}

leetcode/arrays/java/two-sum.java

@@ -0,0 +1,41 @@
+// Solution 1: Brute Force
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        int n = nums.length;
+        for(int i = 0; i < n-1; i++)
+        {
+            for(int j = i + 1; j < n; j++)
+            {
+                if(nums[i] + nums[j] == target)
+                {
+                    return new int[]{i,j};
+                }
+            }
+        }
+        return new int[]{};
+    }
+}
+
+// Solution 2: Hash Table
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer,Integer> index_mapping = new HashMap<>();
+        int list_len = nums.length;
+
+        // Map element with its index in hash table
+        for(int i = 0; i < list_len; i++)
+        {
+            index_mapping.put(nums[i],i);
+        }
+
+        for(int i = 0; i < list_len-1; i++)
+        {
+            int second_element = target - nums[i];
+            if(index_mapping.containsKey(second_element) && index_mapping.get(second_element) != i)
+            {
+                return new int[]{i, index_mapping.get(second_element)};
+            }
+        }
+        return new int[]{};
+    }
+}

leetcode/arrays/python/two-sum.py

@@ -0,0 +1,22 @@
+# Solution 1: Brute Force
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        for i in range(0,len(nums)-1):
+            for j in range(i+1,len(nums)):
+                if nums[i] + nums[j] == target:
+                    return [i,j]
+
+# Solution 2: Hash Table          
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        index_mapping = {}
+        list_len = len(nums)
+        # Map element with its index in hash table
+        for i in range(list_len):
+            index_mapping[nums[i]] = i
+        
+        for i in range(list_len):
+            second_element = target - nums[i]
+            if second_element in index_mapping and index_mapping[second_element] != i:
+                return [i,index_mapping[second_element]]
+        return []