帮助搜索二维数组 (Java)

Question

我完全迷路了。我已经在谷歌上搜索了这个问题可能 30 分钟，但我找不到任何特定于 java 的解决方案（或任何交叉到 java 的解决方案）。

我尝试使用通用的两个简单 for 循环来遍历每个单独的字符串，但它似乎只在搜索词位于数组的第一列时才返回结果。

    public static String search(String term) {
        String result = "";
        int row = db.bookdb.length;

        for (int i=0; i<db.bookdb.length; i++) {
            for (int j=0; j<4; j++) {
                if (term.equals(db.bookdb[i][j])) {
                     row = i;
                     break;
                }
            }
        }

        if (row == db.bookdb.length) {
            result += "Your search failed to return any results";
        }
        else {
            for (int j=0; j<4; j++) {
                result += db.bookdb[row][j] + "    ";
            }
        }

        return result;
    }

db 是我正在使用的对象，而 bookdb 是所述对象中的二维数组。 （是的，列数始终为 4）

如果你们需要任何其他信息，请随时询问。

Answer 1

您的搜索方法效果很好。我创建了一个类并使用了您的搜索方法（复制并粘贴，我什至没有更改您的搜索）并且它有效。这让我相信问题在于您输入数据的方式。

class Pdeuchler {

    static Pdeuchler db;

    String[][] bookdb;


    public static String search(String term) {
        String result = "";
        int row = db.bookdb.length;

        outer_loop: // CHANGE #1 added a named loop
        for (int i=0; i<db.bookdb.length; i++) {
            for (int j=0; j<4; j++) {
                if (term.equals(db.bookdb[i][j])) {
                     row = i;
                     //break; //REMOVED
                     break outer_loop; // CHANGE #2 breaking to the outer_loop
                }
            }
        }

        if (row == db.bookdb.length) {
            result += "Your search failed to return any results";
        }
        else {
            for (int j=0; j<4; j++) {
                result += db.bookdb[row][j] + "    ";
            }
        }

        return result;
    }

    public static void main(String[] args) {
        db = new Pdeuchler();
        db.bookdb = new String[10][4]; // title, author, publisher, year

        db.bookdb[0] = new String[] {"Awesome Book","Stan","West","2001"};
        db.bookdb[1] = new String[] {"Cool Story","Dan","North","2002"};
        db.bookdb[2] = new String[] {"Brothers","North","North","2003"};
        db.bookdb[3] = new String[] {"Never again!","Bob","West","2004"};
        db.bookdb[4] = new String[] {"Howdy Partner","Stan","South","2005"};
        db.bookdb[5] = new String[] {"What the StackOverflow?","Dan","North","2006"};
        db.bookdb[6] = new String[] {"That's hilarious","Angie","South","2007"};
        db.bookdb[7] = new String[] {"I like pie","Angie","East","2008"};
        db.bookdb[8] = new String[] {"Bob writes a book","Bob","South","2009"};
        db.bookdb[9] = new String[] {"The adverntures of Bob","Bob","North","2010"};

        System.out.println(search("I like pie"));
        System.out.println(search("North"));
        System.out.println(search("Dan"));
    }

}

结果：

C:\junk>java Pdeuchler
I like pie    Angie    East    2008
The adverntures of Bob    Bob    North    2010
What the StackOverflow?    Dan    North    2006

C:\junk>

和变化的结果：

C:\junk>javac Pdeuchler.java

C:\junk>java Pdeuchler
I like pie    Angie    East    2008
Cool Story    Dan    North    2002
Cool Story    Dan    North    2002

C:\junk>

如果我们使用高级搜索方法（我称之为 search2），我们会得到：

C:\junk>java Pdeuchler
simple search:
I like pie    Angie    East    2008
Cool Story    Dan    North    2002
Cool Story    Dan    North    2002

advanced search:
I like pie    Angie    East    2008

Cool Story    Dan    North    2002
Brothers    North    North    2003
What the StackOverflow?    Dan    North    2006
The adverntures of Bob    Bob    North    2010

Cool Story    Dan    North    2002
What the StackOverflow?    Dan    North    2006


C:\junk>

这是高级搜索方法：

public static String search2(String term) {
    String result = "";
    int row = db.bookdb.length;

    for (int i=0; i<db.bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(db.bookdb[i][j])) {
                 row = i;
                 for (int k=0; k<4; k++) {
                     result += db.bookdb[i][k] + "    ";
                 }
                 result += "\n";
                 break; // breaks out of the INNER (j) loop
            }
        }
    }

    if (row == db.bookdb.length) {
        result += "Your search failed to return any results";
    }
    return result;
}

Answer 2

您的“break”语句会从内部循环中中断，但不会从外部循环中中断。改写成这样：

boolean found = false;

for (int i = 0; i < db.bookdb.length && !found; i ++) {
  for (int j=0; j<4 && !found; j++) {
    if (yourCondition) {
      row = i;
      found = true;
    }
  }
}

Answer 3

你确定 db.bookdb.length 不总是 1 吗？

这可能会对您有所帮助：

int[][] 矩阵 = 新的 int[10][30]; System.out.println("行数 = " + matrix.length); System.out.println("列数 = " + matrix[0].length);

Answer 4

我不确定你的 bookdb 是什么类型，但你可以更改它

private static int searchTermInArray(String[][] bookdb, String term) {
    for (int i=0; i<bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(bookdb[i][j])) {
                return i;
            }
        }
    }
    return -1;
}

public static String search(String term) {
    String result = "";
    int row = searchTermInArray(db.bookdb, term);
    if (row == -1) {
        result += "Your search failed to return any results";
    }
    else {
        for (int j=0; j<4; j++) {
            result += db.bookdb[row][j] + "    ";
        }
    }

    return result;
}

Answer 5

你需要打破这两个循环。您可以用“mainfor”标记外部循环，并在中断后使用该标签

public static String search(String term) {
    String result = "";
    int row = db.bookdb.length;

    mainfor: for (int i=0; i<db.bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(db.bookdb[i][j])) {
                 row = i;
                 break mainfor;
            }
        }
    }
 ... //rest of your code as is
}