MatrixProblems

MatrixMultiplication.java

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+import java.util.Scanner;
+
+public class MatrixMultiplication {
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        int n1 = scanner.nextInt();
+        int m1 = scanner.nextInt();
+
+        int [][] a1 = new int [n1][m1];
+
+        for(int i =0; i<n1; i++)
+        {
+            for(int j =0; j<m1; j++)
+            {
+                a1[i][j]= scanner.nextInt();
+            }
+        }
+
+        int n2 = scanner.nextInt();
+        int m2 = scanner.nextInt();
+
+        int [][] a2 = new int [n2][m2];
+
+        for(int i =0; i<n2; i++)
+        {
+            for(int j =0; j<m2; j++)
+            {
+                a2[i][j]= scanner.nextInt();
+            }
+        }
+
+        if(m1==n2)
+        {
+            int [][] num = new int [n1][m2];
+            int sum;
+            for(int i =0; i<n1; i++)
+            {
+                for(int j =0; j<m2; j++)
+                {
+                    sum=0;
+                    for(int k=0; k<m1; k++)
+                    {
+                        sum+= a1[i][k]* a2[k][j];
+                    }
+
+                    num[i][j]= sum;
+                }
+            }
+
+
+            // System.out.println("printing array");
+            for(int i =0; i<n1; i++)
+            {
+                for(int j =0; j<m2; j++)
+                {
+                    System.out.print(num[i][j]+" ");
+                }
+                System.out.println();
+            }
+        }
+        else
+        {
+            System.out.println("Invalid input");
+        }
+
+    }
+}

MatrixSpiralTraversal.java

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+import java.util.Scanner;
+
+public class MatrixSpiralTraversal {
+
+    public static void main(String [] args)
+    {
+        Scanner scanner = new Scanner(System.in);
+        int n = scanner.nextInt();
+        int m = scanner.nextInt();
+
+        int [][] arr = new int [n][m];
+
+        for(int i =0; i<n; i++)
+        {
+            for(int j =0; j<m; j++)
+            {
+                arr[i][j]= scanner.nextInt();
+            }
+        }
+
+        System.out.println("PRINTING ARRAY");
+        int leastRow = 0;
+        int leastCol =0;
+        int maxRow = n-1;
+        int maxCol = m-1;
+        int entries = n*m;
+        int count =0;
+
+        while(count<entries)
+        {
+            //Print left column
+            for(int i =leastRow; i<=maxRow && count<entries; i++)// 0-4
+            {
+                System.out.println(arr[i][leastCol]);
+                count++;
+            }
+            leastCol++;
+
+            //Print bottom row
+            for(int i =leastCol; i<=maxCol && count<entries ; i++)
+            {
+                System.out.println(arr[maxRow][i]);
+                count++;
+            }
+            maxRow--;
+
+            //Print right column
+            for(int i =maxRow; i>=leastRow && count<entries; i--)
+            {
+                System.out.println(arr[i][maxCol]);
+                count++;
+            }
+            maxCol--;
+
+            //Print top row
+            for(int i =maxCol; i>=leastCol && count<entries ; i--)
+            {
+                System.out.println(arr[leastRow][i]);
+                count++;
+            }
+            leastRow++;
+
+          //  System.out.println("count after box is: "+count);
+        }
+
+    }
+}

MatrixWaveTraversal.java

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+import java.util.Scanner;
+
+public class MatrixWaveTraversal {
+    public static void main(String [] args)
+    {
+        Scanner scanner = new Scanner(System.in);
+        int n = scanner.nextInt();
+        int m = scanner.nextInt();
+
+        int [][] arr = new int [n][m];
+
+        for(int i =0; i<n; i++)
+        {
+            for(int j =0; j<m; j++)
+            {
+                arr[i][j]= scanner.nextInt();
+            }
+        }
+
+       // System.out.println("PRINTING ARRAY");
+        int j =0;
+        for(int i =0; i<m ; i++)
+        {
+
+            if(i%2!=0)
+            {
+                while(j>0)
+                {
+                    System.out.println(arr[--j][i]);
+                }
+            }
+            else
+            {
+                while(j<n)
+                {
+                    System.out.println(arr[j++][i]);
+                }
+            }
+        }
+
+    }
+}