Update MatrixChainMultiplication.java

Dynamic Programming/MatrixChainMultiplication.java

@@ -1,7 +1,8 @@
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Scanner;
 
-public class MatrixChainMultiplicationTest {
+public class MatrixChainMultiplication {
     private static Scanner scan = new Scanner(System.in);
     private static ArrayList<Matrix> mArray = new ArrayList<>();
     private static int size;
@@ -11,17 +12,17 @@ public class MatrixChainMultiplicationTest {
 
     public static void main(String[] args) {
         int count = 1;
-		while(true) {
+        while (true) {
-			String [] mSize = input("input size of matrix A("+count+") ( ex. 10 20 ) : ");
+            String[] mSize = input("input size of matrix A(" + count + ") ( ex. 10 20 ) : ");
             int col = Integer.parseInt(mSize[0]);
-			if (col==0) break;
+            if (col == 0) break;
             int row = Integer.parseInt(mSize[1]);
 
             Matrix matrix = new Matrix(count, col, row);
             mArray.add(matrix);
             count++;
         }
-		for(Matrix m : mArray) {
+        for (Matrix m : mArray) {
             System.out.format("A(%d)  =  %2d  x  %2d\n", m.count(), m.col(), m.row());
         }
 
@@ -30,35 +31,36 @@ public class MatrixChainMultiplicationTest {
         s = new int[size + 1][size + 1];
         p = new int[size + 1];
 
-		for (int i=0; i<size+1; i++) {
+        for (int i = 0; i < size + 1; i++) {
-			for (int j=0; j<size+1; j++) {
+            Arrays.fill(m[i], -1);
-				m[i][j] = -1;
+            Arrays.fill(s[i], -1);
-				s[i][j] = -1;
-			}
         }
 
-		for (int i=0; i<p.length; i++) {
+        for (int i = 0; i < p.length; i++) {
-			if (i == 0) {
+            p[i] = i == 0 ? mArray.get(i).col() : mArray.get(i - 1).row();
-				p[i] = mArray.get(i).col();
-			} else {
-				p[i] = mArray.get(i-1).row();
-			}
         }
 
         matrixChainOrder();
-		for(int i=0; i<size; i++) { System.out.print("-------"); }
+        for (int i = 0; i < size; i++) {
+            System.out.print("-------");
+        }
         System.out.println();
         printArray(m);
-		for(int i=0; i<size; i++) { System.out.print("-------"); }
+        for (int i = 0; i < size; i++) {
+            System.out.print("-------");
+        }
         System.out.println();
         printArray(s);
-		for(int i=0; i<size; i++) { System.out.print("-------"); }
+        for (int i = 0; i < size; i++) {
+            System.out.print("-------");
+        }
         System.out.println();
 
-		System.out.println("Optimal solution : "+ m[1][size]);
+        System.out.println("Optimal solution : " + m[1][size]);
         System.out.print("Optimal parens : ");
         printOptimalParens(1, size);
     }
+
     private static void printOptimalParens(int i, int j) {
         if (i == j) {
             System.out.print("A" + i);
@@ -69,9 +71,10 @@ public class MatrixChainMultiplicationTest {
             System.out.print(")");
         }
     }
+
     private static void printArray(int[][] array) {
-		for (int i = 1; i < size+1; i++) {
+        for (int i = 1; i < size + 1; i++) {
-			for (int j = 1; j < size+1; j++) {
+            for (int j = 1; j < size + 1; j++) {
                 System.out.print(String.format("%7d", array[i][j]));
             }
             System.out.println();
@@ -79,17 +82,17 @@ public class MatrixChainMultiplicationTest {
     }
 
     private static void matrixChainOrder() {
-		for (int i = 1; i<size+1; i++) {
+        for (int i = 1; i < size + 1; i++) {
             m[i][i] = 0;
         }
 
-		for (int l = 2; l <size+1; l++) {
+        for (int l = 2; l < size + 1; l++) {
-			for (int i = 1; i<size-l+2; i++) {
+            for (int i = 1; i < size - l + 2; i++) {
-				int j = i+l-1;
+                int j = i + l - 1;
                 m[i][j] = Integer.MAX_VALUE;
 
                 for (int k = i; k < j; k++) {
-					int q = m[i][k] + m[k+1][j] + p[i-1] * p[k] * p[j];
+                    int q = m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j];
                     if (q < m[i][j]) {
                         m[i][j] = q;
                         s[i][j] = k;
@@ -101,20 +104,31 @@ public class MatrixChainMultiplicationTest {
 
     private static String[] input(String string) {
         System.out.print(string);
-		return (scan.nextLine().split(" ") );
+        return (scan.nextLine().split(" "));
     }
 
 }
+
 class Matrix {
     private int count;
     private int col;
     private int row;
-	public Matrix(int count, int col, int row) {
+
+    Matrix(int count, int col, int row) {
         this.count = count;
         this.col = col;
         this.row = row;
     }
-	public int count() { return this.count; }
+
-	public int col() { return this.col; }
+    int count() {
-	public int row() { return this.row; }
+        return count;
+    }
+
+    int col() {
+        return col;
+    }
+
+    int row() {
+        return row;
+    }
 }