Added codes for 31 May

GeeksForGeeks/May/31-5-24/GFG.java

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+//{ Driver Code Starts
+// Initial Template for Java
+import java.io.*;
+import java.util.*;
+
+class GFG {
+    public static void main(String args[]) throws IOException {
+        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
+        int t = Integer.parseInt(read.readLine());
+        while (t-- > 0) {
+            int n = Integer.parseInt(read.readLine());
+            Solution ob = new Solution();
+            System.out.println(ob.swapNibbles(n));
+        }
+    }
+}
+// } Driver Code Ends
+
+
+// User function Template for Java
+class Solution {
+    static int swapNibbles(int n) {
+        // code here
+        return ((n & 0x0F) << 4 | (n & 0xF0) >> 4);
+    }
+}

GeeksForGeeks/May/31-5-24/README.md

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+Time complexity - O(1)
+Space complexity - O(1)

LeetCode/May/31-5-24/README.md

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+Time complexity - O(n)
+Space complexity - O(1)

LeetCode/May/31-5-24/Solution.java

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+class Solution 
+{
+    public int[] singleNumber(int[] nums) 
+    {
+        int xors = Arrays.stream(nums).reduce((a, b) -> a ^ b).getAsInt();
+        int lowbit = xors & -xors;
+        int[] ans = new int[2];
+
+        // Seperate `nums` into two groups by `lowbit`.
+        for (int num : nums)
+        {
+            if ((num & lowbit) > 0)
+                ans[0] ^= num;
+            else
+                ans[1] ^= num;
+        }
+
+        return ans;
+    }
+}