Java/DynamicProgramming/MatrixChainMultiplication.java at master · foresightyj/Java · GitHub

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package DynamicProgramming;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Scanner;

public class MatrixChainMultiplication {

private static Scanner scan = new Scanner(System.in);

private static ArrayList<Matrix> mArray = new ArrayList<>();

private static int size;

private static int[][] m;

private static int[][] s;

private static int[] p;

public static void main(String[] args) {

int count = 1;

while (true) {

String[] mSize = input("input size of matrix A(" + count + ") ( ex. 10 20 ) : ");

int col = Integer.parseInt(mSize[0]);

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) {

System.out.format("A(%d) = %2d x %2d%n", m.count(), m.col(), m.row());

}

size = mArray.size();

m = new int[size + 1][size + 1];

s = new int[size + 1][size + 1];

p = new int[size + 1];

for (int i = 0; i < size + 1; i++) {

Arrays.fill(m[i], -1);

Arrays.fill(s[i], -1);

}

for (int i = 0; i < p.length; i++) {

p[i] = i == 0 ? mArray.get(i).col() : mArray.get(i - 1).row();

}

matrixChainOrder();

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("-------");

}

System.out.println();

printArray(s);

for (int i = 0; i < size; i++) {

System.out.print("-------");

}

System.out.println();

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);

} else {

System.out.print("(");

printOptimalParens(i, s[i][j]);

printOptimalParens(s[i][j] + 1, j);

System.out.print(")");

}

private static void printArray(int[][] array) {

for (int i = 1; i < size + 1; i++) {

for (int j = 1; j < size + 1; j++) {

System.out.print(String.format("%7d", array[i][j]));

}

System.out.println();

}

private static void matrixChainOrder() {

for (int i = 1; i < size + 1; i++) {

m[i][i] = 0;

}

for (int l = 2; l < size + 1; l++) {

for (int i = 1; i < size - l + 2; i++) {

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];

if (q < m[i][j]) {

m[i][j] = q;

s[i][j] = k;

}

private static String[] input(String string) {

System.out.print(string);

return (scan.nextLine().split(" "));

}

class Matrix {

private int count;

private int col;

private int row;

Matrix(int count, int col, int row) {

this.count = count;

this.col = col;

this.row = row;

}

int count() {

return count;

}

int col() {

return col;

}

int row() {

return row;

}

Java/DynamicProgramming/MatrixChainMultiplication.java at master · foresightyj/Java · GitHub

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