Added codes for 23 April

GeeksForGeeks/April/23-4-24/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.firstElement(n));
+        }
+    }
+}
+// } Driver Code Ends
+
+
+// User function Template for Java
+class Solution 
+{
+    static int firstElement(int n) 
+    {
+        // code here
+        int mod = 1000000007;
+
+        if(n <= 2)
+        {
+            return 1;
+        }
+
+        int first = 1;
+        int second = 1;
+        int res = 0;
+
+        for(int i = 0 ; i < n -2; i++)
+        {
+            res = (first + second) % mod;
+            first = second;
+            second = res;
+        }
+
+        return res % mod;
+    }
+}

GeeksForGeeks/April/23-4-24/README.md

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

LeetCode/April/23-4-24/README.md

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

LeetCode/April/23-4-24/Solution.java

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+class Solution 
+{
+    public List<Integer> findMinHeightTrees(int n, int[][] edges) 
+    {
+        if (n == 0 || edges.length == 0)
+            return new ArrayList<>(Arrays.asList(0));
+
+        List<Integer> ans = new ArrayList<>();
+        Map<Integer, Set<Integer>> graph = new HashMap<>();
+
+        for (int i = 0; i < n; ++i)
+            graph.put(i, new HashSet<>());
+
+        for (int[] edge : edges) 
+        {
+            int u = edge[0];
+            int v = edge[1];
+            graph.get(u).add(v);
+            graph.get(v).add(u);
+        }
+
+        for (Map.Entry<Integer, Set<Integer>> entry : graph.entrySet()) 
+        {
+            int label = entry.getKey();
+            Set<Integer> children = entry.getValue();
+
+            if (children.size() == 1)
+                ans.add(label);
+        }
+
+        while (n > 2) 
+        {
+            n -= ans.size();
+            List<Integer> nextLeaves = new ArrayList<>();
+
+            for (int leaf : ans) 
+            {
+                int u = (int) graph.get(leaf).iterator().next();
+                graph.get(u).remove(leaf);
+
+                if (graph.get(u).size() == 1)
+                    nextLeaves.add(u);
+            }
+
+            ans = nextLeaves;
+        }
+
+        return ans;
+    }
+}