Merge pull request #99 from Ln11211/diagonal

Diagonal

Author: SarthakKeshari

GeeksForGeeks/diagonal.java

@@ -0,0 +1,85 @@
+/* Given a 2D matrix, print all elements of the given matrix in diagonal order.
+For example, consider the following 5 X 4 input matrix.
+Example:
+
+1   2   3   4
+5   6   7   8
+9  10  11  12
+13 14  15  16
+17 18  19  20
+
+Diagonal printing of the above matrix is
+
+1
+5 2
+9 6 3
+13 10 7 4
+17 14 11 8
+18 15 12
+19 16
+20 */
+
+import java.io.*;
+class diagonal
+{
+    int [][]a;
+    int p,q;
+    diagonal() // A constructor
+    {
+        p=0;
+        q=0;
+    }
+    void input ()throws IOException  // A method to input the array order and elements.
+    {    InputStreamReader inp=new InputStreamReader(System.in); 
+         BufferedReader br=new BufferedReader(inp);
+         System.out.println("Enter the matrix order of the matrix");
+         p=Integer.parseInt(br.readLine());
+         q=Integer.parseInt(br.readLine());
+         a=new int[p][q]; // creating a 2D array.
+        System.out.println("now enter the matrix elements");
+        for(int i=0;i<p;i++)
+         {
+            for(int j=0;j<q;j++)
+            { a[i][j]=Integer.parseInt(br.readLine()); }
+           }
+          System.out.println("the matrix elements are"); 
+         for(int i=0;i<p;i++)
+         {
+            for(int j=0;j<q;j++)
+            { System.out.print(a[i][j]+"\t");}
+            System.out.println("\n");
+          }
+        }
+    void logic() // A method to print the diagonal elements.. 
+    {
+     /* The logic() method prints the elements on the diagonal one by one using their index positions 
+        Firstly starting with the number in the top most left corner. Then the number below it and the
+        number diagonaly oposite to it is printed, thus moving diagonaly from left to right.
+        */ 
+        
+       System.out.println("The diagonal elements of the matrix are"); 
+      for(int i=0;i<p;i++)                         //This part of the for loop prints diagonal elements..
+      {   int j=i;                                //until the principal diagonal(including elements on principal diagonal..
+          for(int x=0;x<=i && x<q;x++,j--)
+          {
+             System.out.print(a[j][x]+"\t");     
+            }
+         System.out.println();
+    }
+     for( int i=1;i<q;i++)                          //This part is for the elements that are below the principal diagonal... 
+     {
+         int j=p-1;
+       for(int x=i;x<q;x++,j--)                   //Doing a dry run of the code with some smaple inputs
+          {                                      // is suggested for understanding the logic() method
+             System.out.print(a[j][x]+"\t");
+            }
+            System.out.println();
+    }
+}
+public static void main(String[] args)throws IOException
+ {  
+    diagonal obj= new diagonal();
+    obj.input();
+    obj.logic();
+ }
+}

GeeksForGeeks/welcome.txt

@@ -0,0 +1 @@
+hello