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--- zh:courses:java2025:ch05 [2025/03/16 20:47]
pzczxs [课件]
+++ zh:courses:java2025:ch05 [2025/04/04 11:26] (当前版本)
pzczxs 讨论状态变化了
@@ 行 373: / 行 373: @@
 ===== 上机作业 =====
   * 完善Matrix类，补充矩阵转置方法，以及提取特定行与特定列的方法；
+【参考答案】
+<file java Matrix.java>
+package cn.edu.bjut.chapter5;
+public class Matrix {
+	private double[][] values;
+	private int nrows, ncols;
+	public Matrix(int nrows, int ncols) {
+		this.nrows = nrows;
+		this.ncols = ncols;
+		this.values = new double[nrows][ncols];
+	}
+	public Matrix(double[][] values) {
+		this.nrows = values.length;
+		this.ncols = values[0].length;
+		this.values = values;
+	}
+	public Matrix add(Matrix mat) {
+		if (nrows != mat.nrows || ncols != mat.ncols) {
+			return null;
+		}
+		double[][] newValues = new double[nrows][ncols];
+		for (int i = 0; i < nrows; i++) {
+			for (int j = 0; j < ncols; j++) {
+				newValues[i][j] = values[i][j] + mat.values[i][j];
+			}
+		}
+		return (new Matrix(newValues));
+	}
+	public Matrix substract(Matrix mat) {
+		if (nrows != mat.nrows || ncols != mat.ncols) {
+			return null;
+		}
+		double[][] newValues = new double[nrows][ncols];
+		for (int i = 0; i < nrows; i++) {
+			for (int j = 0; j < ncols; j++) {
+				newValues[i][j] = values[i][j] - mat.values[i][j];
+			}
+		}
+		return (new Matrix(newValues));
+	}
+	public Matrix multiplicate(Matrix mat) {
+		if (ncols != mat.nrows) {
+			return null;
+		}
+		double[][] newValues = new double[nrows][mat.ncols];
+		for (int i = 0; i < nrows; i++) {
+			for (int j = 0; j < mat.ncols; j++) {
+				double sum = 0;
+				for (int k = 0; k < ncols; k++) {
+					sum += values[i][k] * mat.values[k][j];
+				}
+				newValues[i][j] = sum;
+			}
+		}
+		return (new Matrix(newValues));
+	}
+	public Matrix transpose() {
+		double[][] newValues = new double[ncols][nrows];
+		for (int i = 0; i < nrows; i++) {
+			for (int j = 0; j < ncols; j++) {
+				newValues[j][i] = values[i][j];
+			}
+		}
+		return (new Matrix(newValues));
+	}
+	public Matrix getColumn(int idx) {
+		if (idx < 0 || idx >= ncols) {
+			return null;
+		}
+		double[][] colVector = new double[nrows][1];
+		for (int i = 0; i < nrows; i++) {
+			colVector[i][0] = values[i][idx];
+		}
+		return new Matrix(colVector);
+	}
+	public Matrix getRow(int idx) {
+		if (idx < 0 || idx >= nrows) {
+			return null;
+		}
+		double[][] rowVector = new double[1][ncols];
+		for (int j = 0; j < ncols; j++) {
+			rowVector[0][j] = values[idx][j];
+		}
+		return new Matrix(rowVector);
+	}
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < nrows; i++) {
+			for (int j = 0; j < ncols; j++) {
+				sb.append("\t" + values[i][j]);
+			}
+			sb.append("\n");
+		}
+		return sb.toString();
+	}
+}
+</file>
   * 写一个类CharCounter，当给定一个字符串时，可以统计其中英文字母及数字出现的频次，并且可以查询特定字符出现在的频次；
+【参考答案】
+<file java CharCounter.java>
+package cn.edu.bjut.chapter5;
+public class CharCounter {
+	private int[] count;
+	public CharCounter(String str) {
+		this.count = new int[26 + 10];
+		str = str.toLowerCase();
+		for (int i = 0; i < str.length(); i++) {
+			char c = str.charAt(i);
+			if (c >= 'a' && c <= 'z') {
+				int idx = c - 'a';
+				count[idx]++;
+			} else if (c >= '0' && c <= '9') {
+				int idx = c - '0' + 26;
+				count[idx]++;
+			}
+		}
+	}
+	public int getCount(char ch) {
+		if (ch >= 'a' && ch <= 'z') {
+			int idx = ch - 'a';
+			return count[idx];
+		} else if (ch >= '0' && ch <= '9') {
+			int idx = ch - '0' + 26;
+			return count[idx];
+		}
+		return -1; //无效字符
+	}
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < count.length; i++) {
+			if (count[i] == 0) {
+				continue;
+			}
+			char c = (i < 26) ? (char) (i + 'a') : (char) (i - 26 + '0');
+			sb.append(c + ": " + count[i] + "\n");
+		}
+		return sb.toString();
+	}
+	public static void main(String[] args) {
+		String str = "abcBCD.-,1234321我们";
+		CharCounter counter = new CharCounter(str);
+		System.out.println(counter);
+		// 也可以直接得到某个字符出现的频次
+		System.out.println("a: " + counter.getCount('a'));
+	}
+}
+</file>
   * 给定五篇专利文献，每篇专利文献的信息见下表，在上次课程作业的基础上，将这五篇专利文献存放在数组中。
@@ 行 382: / 行 566: @@
 | 14711011               | 2015-05-13              | B32B  17/10, B32B  27/32                 | G06F   3/485                                               | L         | A      |
 | 14515267               | 2014-10-15              | F16F  15/02, G09G   5/34, G06F   3/0485  | A01B  15/06, A01B  15/06                                   | L         | I      |
+【参考答案】
+<file java Classification.java>
+package cn.edu.bjut.chapter5;
+public class Classification {
+	protected char section;
+	protected int mainClass;
+	protected char subclass;
+	protected int mainGroup;
+	protected int subgroup;
+	public final static char SEPARATOR = '/';
+	public Classification(char section, int mainClass, char subclass, int mainGroup, int subgroup) {
+		this.section = section;
+		this.mainClass = mainClass;
+		this.subclass = subclass;
+		this.mainGroup = mainGroup;
+		this.subgroup = subgroup;
+	}
+	// example: G09F 17/30
+	public Classification(String symbol) {
+		this.section = symbol.charAt(0);
+		this.mainClass = Integer.parseInt(symbol.substring(1, 3));
+		this.subclass = symbol.charAt(3);
+		int pos = symbol.indexOf(SEPARATOR);
+		this.mainGroup = Integer.parseInt(symbol.substring(4, pos).trim());
+		this.subgroup = Integer.parseInt(symbol.substring(pos + 1));
+	}
+	public char getSection() {
+		return section;
+	}
+	public void setSection(char section) {
+		this.section = section;
+	}
+	public int getMainClass() {
+		return mainClass;
+	}
+	public void setMainClass(int mainClass) {
+		this.mainClass = mainClass;
+	}
+	public char getSubclass() {
+		return subclass;
+	}
+	public void setSubclass(char subclass) {
+		this.subclass = subclass;
+	}
+	public int getMainGroup() {
+		return mainGroup;
+	}
+	public void setMainGroup(int mainGroup) {
+		this.mainGroup = mainGroup;
+	}
+	public int getSubgroup() {
+		return subgroup;
+	}
+	public void setSubgroup(int subgroup) {
+		this.subgroup = subgroup;
+	}
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append(section);
+		sb.append(String.format("%2s", mainClass).replace(' ', '0'));
+		sb.append(subclass);
+		sb.append(String.format("%4s", mainGroup));
+		sb.append(SEPARATOR);
+		sb.append(subgroup);
+		return sb.toString();
+	}
+}
+</file>
+<file java Ipc.java>
+package cn.edu.bjut.chapter5;
+public class Ipc extends Classification {
+	public Ipc(char section, int mainClass, char subclass, int mainGroup, int subgroup) {
+		super(section, mainClass, subclass, mainGroup, subgroup);
+	}
+	public Ipc(String symbol) {
+		super(symbol);
+	}
+	public static void main(String[] args) {
+		char section = 'A';
+		int mainClass = 4;
+		char subclass = 'B';
+		int mainGroup = 55;
+		int subgroup = 56;
+		Classification ipc = new Ipc(section, mainClass, subclass, mainGroup, subgroup);
+		System.out.println(ipc);
+		String symbol = "G09F 17/30";
+		System.out.println(new Ipc(symbol));
+	}
+}
+</file>
+<file java Cpc.java>
+package cn.edu.bjut.chapter5;
+public class Cpc extends Classification {
+	private char position;
+	private char value;
+	public Cpc(char section, int mainClass, char subclass, int mainGroup, int subgroup, char position, char value) {
+		super(section, mainClass, subclass, mainGroup, subgroup);
+		this.position = position;
+		this.value = value;
+	}
+	public Cpc(String symbol, char position, char value) {
+		super(symbol);
+		this.position = position;
+		this.value = value;
+	}
+	public char getPosition() {
+		return position;
+	}
+	public void setPosition(char position) {
+		this.position = position;
+	}
+	public char getValue() {
+		return value;
+	}
+	public void setValue(char value) {
+		this.value = value;
+	}
+}
+</file>
+<file java Date.java>
+package cn.edu.bjut.chapter5;
+public class Date {
+	private int year, month, day;
+	public Date(int year, int month, int day) {
+		this.year = year;
+		this.month = month;
+		this.day = day;
+	}
+	// format: YYYY-MM-DD
+	public Date(String str) {
+		String[] parts = str.trim().split("-");
+		this.year = Integer.parseInt(parts[0]);
+		this.month = Integer.parseInt(parts[1]);
+		this.day = Integer.parseInt(parts[2]);
+	}
+	public int getYear() {
+		return year;
+	}
+	public void setYear(int year) {
+		this.year = year;
+	}
+	public int getMonth() {
+		return month;
+	}
+	public void setMonth(int month) {
+		this.month = month;
+	}
+	public int getDay() {
+		return day;
+	}
+	public void setDay(int day) {
+		this.day = day;
+	}
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append(year);
+		if (month < 10) {
+			sb.append("0" + month);
+		} else {
+			sb.append(month);
+		}
+		if (day < 10) {
+			sb.append("0" + day);
+		} else {
+			sb.append(day);
+		}
+		return sb.toString();
+	}
+}
+</file>
+<file java Patent.java>
+package cn.edu.bjut.chapter5;
+public class Patent {
+	private String applicationNo;
+	private Date applicationDate;
+	private Ipc[] ipcs;
+	private Cpc[] cpcs;
+	private final static String SEPERATOR = ",";
+	public Patent(String applicationNo, Date applicationDate, Ipc[] ipcs, Cpc[] cpcs) {
+		this.applicationNo = applicationNo;
+		this.applicationDate = applicationDate;
+		this.ipcs = ipcs;
+		this.cpcs = cpcs;
+	}
+	public Patent(String applicationNo, String applicationDate, String multiIpcs, String multiCpcs, char position, char value) {
+		this.applicationNo = applicationNo;
+		this.applicationDate = new Date(applicationDate);
+		String[] ipcSymbols = multiIpcs.split(SEPERATOR);
+		this.ipcs = new Ipc[ipcSymbols.length];
+		for (int i = 0; i < ipcSymbols.length; i++) {
+			ipcs[i] = new Ipc(ipcSymbols[i].trim());
+		}
+		String[] cpcSymbols = multiCpcs.split(SEPERATOR);
+		this.cpcs = new Cpc[cpcSymbols.length];
+		for (int i = 0; i < cpcSymbols.length; i++) {
+			cpcs[i] = new Cpc(cpcSymbols[i].trim(), position, value);
+		}
+	}
+	public String getApplicationNo() {
+		return applicationNo;
+	}
+	public void setApplicationNo(String applicationNo) {
+		this.applicationNo = applicationNo;
+	}
+	public Date getApplicationDate() {
+		return applicationDate;
+	}
+	public void setApplicationDate(Date applicationDate) {
+		this.applicationDate = applicationDate;
+	}
+	public Ipc[] getIpcs() {
+		return ipcs;
+	}
+	public void setIpcs(Ipc[] ipcs) {
+		this.ipcs = ipcs;
+	}
+	public Cpc[] getCpcs() {
+		return cpcs;
+	}
+	public void setCpcs(Cpc[] cpcs) {
+		this.cpcs = cpcs;
+	}
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append(applicationNo + "\t" + applicationDate + "\t");
+		sb.append("[");
+		for (int i = 0; i < ipcs.length - 1; i++) {
+			sb.append(ipcs[i] + SEPERATOR);
+		}
+		sb.append(ipcs[ipcs.length - 1] + "]\t");
+		sb.append("[");
+		for (int i = 0; i < cpcs.length - 1; i++) {
+			sb.append(cpcs[i] + SEPERATOR);
+		}
+		sb.append(cpcs[cpcs.length - 1] + "]");
+		return sb.toString();
+	}
+	public static void main(String[] args) {
+		Patent[] patents = new Patent[5];
+		patents[0] = new Patent("14725838", "2015-05-29", "A23B 5/04, A23B 5/045", "A23B 5/04, A23B 5/45, A23L 15/20", 'F', 'I');
+		patents[1] = new Patent("14814205", "2015-07-30", "A61H 33/00, C01B 33/107, E04B 1/84", "A61H 33/6063, A61H 33/6042", 'F', 'I');
+		patents[2] = new Patent("15189723", "2016-06-22", "D04B 1/00", "B65H2301/44514, C01B 33/1071, F16F 15/2, H01L 27/14641", 'L', 'A');
+		patents[3] = new Patent("14711011", "2015-05-13", "B32B 17/10, B32B 27/32", "G06F 3/485", 'L', 'A');
+		patents[4] = new Patent("14515267", "2014-10-15", "F16F 15/02, G09G 5/34, G06F 3/0485", "A01B 15/06, A01B 15/06", 'L', 'I');
+		for (Patent patent: patents) {
+			System.out.println(patent);
+		}
+	}
+}
+</file>
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+~~DISCUSSION:closed~~

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