Added codes for 13 March

GeeksForGeeks/March/13-3-24/GFG.java

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+//{ Driver Code Starts
+import java.util.*;
+import java.lang.*;
+import java.io.*;
+class GFG
+{
+    public static void main(String[] args) throws IOException
+    {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int T = Integer.parseInt(br.readLine().trim());
+        while(T-->0)
+        {
+            int n = Integer.parseInt(br.readLine().trim());
+            int[][] mat = new int[n][n];
+            String[] S = br.readLine().trim().split(" ");
+            int i = 0;
+            int j = 0;
+            for(int k = 0; k < S.length; k++){
+                mat[i][j] = Integer.parseInt(S[k]);
+                j++;
+                if(j == n){
+                    i++;
+                    j = 0;
+                }
+            }
+            Solution obj = new Solution();
+            int[] ans = obj.matrixDiagonally(mat);
+            for(int it = 0; it < ans.length; it++){
+                System.out.print(ans[it] + " ");
+            }
+            System.out.println();
+        }
+    }
+}
+
+// } Driver Code Ends
+
+
+class Solution 
+{
+    public int[] matrixDiagonally(int[][] mat) 
+    {
+        int n = mat.length, mode = 0, it = 0, lower = 0; 
+        ArrayList<Integer> arr = new ArrayList<>();
+
+        for (int t = 0; t < (2 * n - 1); t++) 
+        { 
+            int t1 = t; 
+            if (t1 >= n) 
+            { 
+                mode++; 
+                t1 = n - 1; 
+                it--; 
+                lower++; 
+            } 
+            else 
+            { 
+                lower = 0; 
+                it++; 
+            } 
+
+            for (int i = t1; i >= lower; i--) 
+            { 
+                if ((t1 + mode) % 2 == 0) 
+                { 
+                    arr.add(mat[i][t1 + lower - i]);
+                } 
+                else
+                { 
+                    arr.add(mat[t1 + lower - i][i]); 
+                } 
+            } 
+        }
+
+        return arr.stream().mapToInt(i -> i).toArray();
+    }
+}

GeeksForGeeks/March/13-3-24/README.md

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+Time complexity - O(n^2)
+Space complexity - O(n)

LeetCode/March/13-3-24/README.md

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

LeetCode/March/13-3-24/Solution.java

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+class Solution 
+{
+    public int pivotInteger(int n) 
+    {
+        int y = (n * n + n) / 2;
+        int x = (int) Math.sqrt(y);
+        return x * x == y ? x : -1;
+    }
+}