137 lines
3.6 KiB
Java
137 lines
3.6 KiB
Java
package DynamicProgramming;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Scanner;
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public class MatrixChainMultiplication {
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private static Scanner scan = new Scanner(System.in);
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private static ArrayList<Matrix> mArray = new ArrayList<>();
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private static int size;
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private static int[][] m;
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private static int[][] s;
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private static int[] p;
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public static void main(String[] args) {
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int count = 1;
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while (true) {
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String[] mSize = input("input size of matrix A(" + count + ") ( ex. 10 20 ) : ");
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int col = Integer.parseInt(mSize[0]);
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if (col == 0) break;
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int row = Integer.parseInt(mSize[1]);
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Matrix matrix = new Matrix(count, col, row);
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mArray.add(matrix);
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count++;
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}
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for (Matrix m : mArray) {
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System.out.format("A(%d) = %2d x %2d%n", m.count(), m.col(), m.row());
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}
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size = mArray.size();
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m = new int[size + 1][size + 1];
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s = new int[size + 1][size + 1];
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p = new int[size + 1];
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for (int i = 0; i < size + 1; i++) {
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Arrays.fill(m[i], -1);
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Arrays.fill(s[i], -1);
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}
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for (int i = 0; i < p.length; i++) {
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p[i] = i == 0 ? mArray.get(i).col() : mArray.get(i - 1).row();
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}
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matrixChainOrder();
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for (int i = 0; i < size; i++) {
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System.out.print("-------");
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}
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System.out.println();
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printArray(m);
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for (int i = 0; i < size; i++) {
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System.out.print("-------");
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}
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System.out.println();
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printArray(s);
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for (int i = 0; i < size; i++) {
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System.out.print("-------");
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}
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System.out.println();
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System.out.println("Optimal solution : " + m[1][size]);
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System.out.print("Optimal parens : ");
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printOptimalParens(1, size);
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}
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private static void printOptimalParens(int i, int j) {
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if (i == j) {
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System.out.print("A" + i);
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} else {
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System.out.print("(");
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printOptimalParens(i, s[i][j]);
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printOptimalParens(s[i][j] + 1, j);
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System.out.print(")");
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}
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}
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private static void printArray(int[][] array) {
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for (int i = 1; i < size + 1; i++) {
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for (int j = 1; j < size + 1; j++) {
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System.out.print(String.format("%7d", array[i][j]));
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}
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System.out.println();
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}
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}
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private static void matrixChainOrder() {
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for (int i = 1; i < size + 1; i++) {
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m[i][i] = 0;
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}
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for (int l = 2; l < size + 1; l++) {
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for (int i = 1; i < size - l + 2; i++) {
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int j = i + l - 1;
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m[i][j] = Integer.MAX_VALUE;
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for (int k = i; k < j; k++) {
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int q = m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j];
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if (q < m[i][j]) {
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m[i][j] = q;
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s[i][j] = k;
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}
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}
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}
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}
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}
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private static String[] input(String string) {
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System.out.print(string);
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return (scan.nextLine().split(" "));
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}
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}
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class Matrix {
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private int count;
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private int col;
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private int row;
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Matrix(int count, int col, int row) {
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this.count = count;
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this.col = col;
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this.row = row;
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}
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int count() {
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return count;
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}
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int col() {
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return col;
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}
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int row() {
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return row;
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}
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}
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