การทำความสะอาดและตรวจสอบข้อมูล 2 มิติ

เหตุใดจึงต้องจัดข้อมูลสองมิติให้สะอาด

ค่าว่างและขอบเขต

public class Main {
  // Make a defensive copy of m. Replace null rows with empty arrays.
  static int[][] copyOrEmpty(int[][] m) {
    if (m == null) return new int[0][0];
    int[][] out = new int[m.length][];
    for (int r = 0; r < m.length; r = r + 1) {
      if (m[r] == null) {
        out[r] = new int[0];
      } else {
        out[r] = new int[m[r].length];
        for (int c = 0; c < m[r].length; c = c + 1) out[r][c] = m[r][c];
      }
    }
    return out;
  }

  // Safe bounds check for jagged matrices
  static boolean inBounds(int[][] m, int r, int c) {
    return m != null && r >= 0 && r < m.length && m[r] != null && c >= 0 && c < m[r].length;
  }

  public static void main(String[] args) {
    int[][] raw = new int[][] { null, {1, 2, 3}, {4} };
    int[][] cleaned = copyOrEmpty(raw);

    System.out.println("rows = " + cleaned.length);
    for (int r = 0; r < cleaned.length; r = r + 1) System.out.println("row " + r + " len = " + cleaned[r].length);

    System.out.println("inBounds(1,2) = " + inBounds(cleaned, 1, 2));  // true
    System.out.println("inBounds(2,2) = " + inBounds(cleaned, 2, 2));  // false
  }
}

จำกัดค่าให้อยู่ในช่วง

public class Main {
  static int clamp(int v, int lo, int hi) { if (v < lo) return lo; if (v > hi) return hi; return v; }
  static void clampAll(int[][] m, int lo, int hi) {
    if (m == null) return;
    for (int r = 0; r < m.length; r = r + 1) {
      if (m[r] == null) continue;
      for (int c = 0; c < m[r].length; c = c + 1) m[r][c] = clamp(m[r][c], lo, hi);
    }
  }
  static void print(int[][] m) {
    for (int r = 0; r < m.length; r = r + 1) {
      if (m[r] == null) { System.out.println("<null row>"); continue; }
      for (int c = 0; c < m[r].length; c = c + 1) System.out.print(m[r][c] + (c + 1 < m[r].length ? " " : ""));
      System.out.println();
    }
  }
  public static void main(String[] args) {
    int[][] m = { { -5, 101, 50 }, null, { 200 } };
    System.out.println("before clamp:");
    print(m);
    clampAll(m, 0, 100);
    System.out.println("after clamp [0..100]:");
    print(m);
  }
}

ปรับรูปทรงให้เป็นมาตรฐาน

public class Main {
  static int[][] padToMaxCols(int[][] m, int pad) {
    if (m == null) return new int[0][0];
    int rows = m.length;
    int maxCols = 0;
    for (int r = 0; r < rows; r = r + 1) if (m[r] != null && m[r].length > maxCols) maxCols = m[r].length;
    int[][] out = new int[rows][maxCols];
    for (int r = 0; r < rows; r = r + 1) {
      int cols = (m[r] == null) ? 0 : m[r].length;
      for (int c = 0; c < cols; c = c + 1) out[r][c] = m[r][c];
      for (int c = cols; c < maxCols; c = c + 1) out[r][c] = pad;  // pad missing cells
    }
    return out;
  }
  static void print(int[][] x) {
    for (int r = 0; r < x.length; r = r + 1) {
      for (int c = 0; c < x[r].length; c = c + 1) System.out.print(x[r][c] + (c + 1 < x[r].length ? " " : ""));
      System.out.println();
    }
  }
  public static void main(String[] args) {
    int[][] jag = { {1, 23, 456}, {7, 8}, null, {90} };
    int[][] rect = padToMaxCols(jag, 0);
    print(rect);
  }
}

รายงานการตรวจสอบความถูกต้อง

public class Main {
  static class Report { int negatives; int overMax; int nullRows; int cells; }
  static Report validate(int[][] m, int hi) {
    Report r = new Report();
    if (m == null) return r;
    for (int i = 0; i < m.length; i = i + 1) {
      if (m[i] == null) { r.nullRows = r.nullRows + 1; continue; }
      for (int j = 0; j < m[i].length; j = j + 1) {
        int v = m[i][j];
        r.cells = r.cells + 1;
        if (v < 0) r.negatives = r.negatives + 1;
        if (v > hi) r.overMax = r.overMax + 1;
      }
    }
    return r;
  }
  public static void main(String[] args) {
    int[][] m = { { -5, 101, 50 }, null, { 200 } };
    Report r = validate(m, 100);
    System.out.println("cells=" + r.cells + ", negatives=" + r.negatives + ", overMax=" + r.overMax + ", nullRows=" + r.nullRows);
  }
}

การพิมพ์โดยข้ามแถวที่เป็นค่าว่าง

public class Main {
  static boolean inBounds(int[][] m, int r, int c) {
    return m != null && r >= 0 && r < m.length && m[r] != null && c >= 0 && c < m[r].length;
  }
  static int[] widths(int[][] m) {
    int maxCols = 0; if (m == null) return new int[0];
    for (int r = 0; r < m.length; r = r + 1) if (m[r] != null && m[r].length > maxCols) maxCols = m[r].length;
    int[] w = new int[maxCols];
    for (int r = 0; r < m.length; r = r + 1) {
      if (m[r] == null) continue;
      for (int c = 0; c < m[r].length; c = c + 1) {
        int len = Integer.toString(m[r][c]).length();
        if (len > w[c]) w[c] = len;
      }
    }
    for (int c = 0; c < w.length; c = c + 1) if (w[c] < 1) w[c] = 1;
    return w;
  }
  static void printAlignedSkipNull(int[][] m) {
    int[] w = widths(m);
    for (int r = 0; r < m.length; r = r + 1) {
      if (m[r] == null) { System.out.println("<skipped null row>"); continue; }
      String line = "";
      for (int c = 0; c < m[r].length; c = c + 1) {
        String s = Integer.toString(m[r][c]);
        while (s.length() < w[c]) s = " " + s;
        line = line + s + (c + 1 < m[r].length ? " " : "");
      }
      System.out.println(line);
    }
  }
  public static void main(String[] args) {
    int[][] m = { { 1, 200, -3 }, null, { 45 } };
    printAlignedSkipNull(m);
  }
}

ตรวจสอบการเข้าถึงอย่างปลอดภัย

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