ฝึกสร้างรูปแบบและโจทย์ท้าทายขนาดเล็ก

เคล็ดลับการสร้างรูปแบบ

สี่เหลี่ยมผืนผ้าโปร่ง

public class Main {
  public static void main(String[] args) {
    // Outer loop: goes through each row (1 to 3)
    for (int r = 1; r <= 3; r = r + 1) {
      String line = "";

      // Inner loop: goes through each column (1 to 5)
      for (int c = 1; c <= 5; c = c + 1) {
        // Print a star if we are on:
        // - the first row (r == 1)
        // - the last row (r == 3)
        // - the first column (c == 1)
        // - the last column (c == 5)
        if (r == 1 || r == 3 || c == 1 || c == 5) {
          line = line + "*";
        } else {
          // Otherwise, print a space (inside of the rectangle)
          line = line + " ";
        }
      }

      // Print the completed row
      System.out.println(line);
    }
  }
}

พีระมิดจัดกึ่งกลาง

public class Main {
  public static void main(String[] args) {
    int h = 4; // height of the pyramid

    // Outer loop: goes through each row (1 to h)
    for (int r = 1; r <= h; r = r + 1) {
      String line = "";

      // First inner loop: add spaces before the stars
      // (h - r) spaces so the stars are centered
      for (int s = 1; s <= (h - r); s = s + 1) {
        line = line + " ";
      }

      // Second inner loop: add stars
      // Formula (2*r - 1) makes the row width odd (1, 3, 5, 7, ...)
      for (int c = 1; c <= (2 * r - 1); c = c + 1) {
        line = line + "*";
      }

      // Print the completed row
      System.out.println(line);
    }
  }
}

เส้นทแยงมุม

public class Main {
  public static void main(String[] args) {
    int n = 4; // size of the square (4 rows and 4 columns)

    // Outer loop: controls rows (1 to n)
    for (int r = 1; r <= n; r = r + 1) {
      String line = "";

      // Inner loop: controls columns (1 to n)
      for (int c = 1; c <= n; c = c + 1) {
        // If row index == column index, print a star
        if (r == c) {
          line = line + "*";
        } else {
          // Otherwise, print a space
          line = line + " ";
        }
      }

      // Print the row
      System.out.println(line);
    }
  }
}

โจทย์ท้าทายขนาดเล็ก

สาธิตรูปแบบ

public class Main {
  public static void main(String[] args) {
    // 1) Hollow rectangle 3x5
    for (int r = 1; r <= 3; r = r + 1) {
      String line = "";
      for (int c = 1; c <= 5; c = c + 1) {
        if (r == 1 || r == 3 || c == 1 || c == 5) line = line + "*";
        else line = line + " ";
      }
      System.out.println(line);
    }

    // 2) Centered pyramid height 4
    int h = 4;
    for (int r = 1; r <= h; r = r + 1) {
      String line = "";
      for (int s = 1; s <= (h - r); s = s + 1) line = line + " ";
      for (int c = 1; c <= (2 * r - 1); c = c + 1) line = line + "*";
      System.out.println(line);
    }

    // 3) Diagonal in a 4x4 square
    int n = 4;
    for (int r = 1; r <= n; r = r + 1) {
      String line = "";
      for (int c = 1; c <= n; c = c + 1) {
        if (r == c) line = line + "*";
        else line = line + " ";
      }
      System.out.println(line);
    }
  }
}

ตรวจสอบสี่เหลี่ยมผืนผ้าโปร่ง

ทบทวนและถัดไป