content: import java.util.Scanner;
  class Strassen
  {
      public int[][] multiply(int[][] A, int[][] B)
      {        
          int n = A.length;
          int[][] R = new int[n][n];
  
          if (n == 1)
              R[0][0] = A[0][0] * B[0][0];
          else
          {
              int[][] A11 = new int[n/2][n/2];
              int[][] A12 = new int[n/2][n/2];
              int[][] A21 = new int[n/2][n/2];
              int[][] A22 = new int[n/2][n/2];
              int[][] B11 = new int[n/2][n/2];
              int[][] B12 = new int[n/2][n/2];
              int[][] B21 = new int[n/2][n/2];
              int[][] B22 = new int[n/2][n/2];
   
              split(A, A11, 0 , 0);
              split(A, A12, 0 , n/2);
              split(A, A21, n/2, 0);
              split(A, A22, n/2, n/2);
   
              split(B, B11, 0 , 0);
              split(B, B12, 0 , n/2);
              split(B, B21, n/2, 0);
              split(B, B22, n/2, n/2);
   
              /** 
                M1 = (A11 + A22)(B11 + B22)
                M2 = (A21 + A22) B11
                M3 = A11 (B12 - B22)
                M4 = A22 (B21 - B11)
                M5 = (A11 + A12) B22
                M6 = (A21 - A11) (B11 + B12)
                M7 = (A12 - A22) (B21 + B22)
              **/
   
              int [][] M1 = multiply(add(A11, A22), add(B11, B22));
              int [][] M2 = multiply(add(A21, A22), B11);
              int [][] M3 = multiply(A11, sub(B12, B22));
              int [][] M4 = multiply(A22, sub(B21, B11));
              int [][] M5 = multiply(add(A11, A12), B22);
              int [][] M6 = multiply(sub(A21, A11), add(B11, B12));
              int [][] M7 = multiply(sub(A12, A22), add(B21, B22));
   
  
                C11 = M1 + M4 - M5 + M7
                C12 = M3 + M5
                C21 = M2 + M4
                C22 = M1 - M2 + M3 + M6
   
              int [][] C11 = add(sub(add(M1, M4), M5), M7);
              int [][] C12 = add(M3, M5);
              int [][] C21 = add(M2, M4);
              int [][] C22 = add(sub(add(M1, M3), M2), M6);
   
              join(C11, R, 0 , 0);
              join(C12, R, 0 , n/2);
              join(C21, R, n/2, 0);
              join(C22, R, n/2, n/2);
          }
  
          return R;
      }
  
      public int[][] sub(int[][] A, int[][] B)
      {
          int n = A.length;
          int[][] C = new int[n][n];
          for (int i = 0; i < n; i++)
              for (int j = 0; j < n; j++)
                  C[i][j] = A[i][j] - B[i][j];
          return C;
      }
      public int[][] add(int[][] A, int[][] B)
      {
          int n = A.length;
          int[][] C = new int[n][n];
          for (int i = 0; i < n; i++)
              for (int j = 0; j < n; j++)
                  C[i][j] = A[i][j] + B[i][j];
          return C;
      }
      public void split(int[][] P, int[][] C, int iB, int jB) 
      {
          for(int i1 = 0, i2 = iB; i1 < C.length; i1++, i2++)
              for(int j1 = 0, j2 = jB; j1 < C.length; j1++, j2++)
                  C[i1][j1] = P[i2][j2];
      }
      
      public void join(int[][] C, int[][] P, int iB, int jB) 
      {
          for(int i1 = 0, i2 = iB; i1 < C.length; i1++, i2++)
              for(int j1 = 0, j2 = jB; j1 < C.length; j1++, j2++)
                  P[i2][j2] = C[i1][j1];
      }    
      
      public static void main (String[] args) 
      {
          Scanner scan = new Scanner(System.in);
          System.out.println("Strassen Multiplication Algorithm Test\n");
      
          Strassen s = new Strassen();
   
          System.out.println("Enter order n :");
          int N = scan.nextInt();
   
          System.out.println("Enter N order matrix 1\n");
          int[][] A = new int[N][N];
          for (int i = 0; i < N; i++)
              for (int j = 0; j < N; j++)
                  A[i][j] = scan.nextInt();
   
          System.out.println("Enter N order matrix 2\n");
          int[][] B = new int[N][N];
          for (int i = 0; i < N; i++)
              for (int j = 0; j < N; j++)
                  B[i][j] = scan.nextInt();
   
          int[][] C = s.multiply(A, B);
   
          System.out.println("\nProduct of matrices A and  B : ");
          for (int i = 0; i < N; i++)
          {
              for (int j = 0; j < N; j++)
                  System.out.print(C[i][j] +" ");
              System.out.println();
          }
   
      }
  }