การแทรก การลบตามดัชนี และการเลื่อน

ภาพรวมการแทรก

แทรกในอาร์เรย์ใหม่

public class Main {
  // Method to insert a value at a given index
  static int[] insertAt(int[] a, int i, int val) {
    // Create a new array, one element larger
    int[] b = new int[a.length + 1];

    // Copy elements before the insertion index
    for (int p = 0; p < i; p = p + 1) {
      b[p] = a[p];
    }

    // Insert the new value at position i
    b[i] = val;

    // Copy the rest of the elements after position i
    for (int p = i; p < a.length; p = p + 1) {
      b[p + 1] = a[p];
    }

    return b;
  }

  public static void main(String[] args) {
    // Example array
    int[] a = {5, 8, 9, 12};

    // Insert 99 at index 2 (between 8 and 9)
    int[] b = insertAt(a, 2, 99);

    // Print new array
    System.out.print("Array after insertion: ");
    for (int x : b) {
      System.out.print(x + " ");
    }
  }
}

ลบและเลื่อน

public class Main {
  // Method to delete an element at index k
  static void deleteAt(int[] a, int k) {
    // Shift elements to the left, starting from index k
    for (int i = k; i < a.length - 1; i = i + 1) {
      a[i] = a[i + 1];
    }

    // Clear the last element (since it's now duplicated)
    a[a.length - 1] = 0; 
  }

  public static void main(String[] args) {
    // Example array
    int[] a = {5, 8, 9, 12, 15};

    // Delete element at index 2 (value = 9)
    deleteAt(a, 2);

    // Print updated array
    System.out.print("Array after deletion: ");
    for (int x : a) {
      System.out.print(x + " ");
    }
  }
}

ตรวจสอบขอบเขต

public class Main {
  // Insert a value at a given index
  static int[] insertAt(int[] a, int i, int val) {
    // Validate index (0 ≤ i ≤ a.length is allowed for insert)
    if (i < 0 || i > a.length) {
      throw new IllegalArgumentException("bad index");
    }

    int[] b = new int[a.length + 1];
    for (int p = 0; p < i; p++) b[p] = a[p];
    b[i] = val;
    for (int p = i; p < a.length; p++) b[p + 1] = a[p];
    return b;
  }

  // Delete a value at a given index
  static void deleteAt(int[] a, int k) {
    // Validate index (0 ≤ k < a.length is required for delete)
    if (k < 0 || k >= a.length) {
      throw new IllegalArgumentException("bad index");
    }

    for (int i = k; i < a.length - 1; i++) {
      a[i] = a[i + 1];
    }
    a[a.length - 1] = 0; // clear the last slot
  }

  public static void main(String[] args) {
    int[] a = {5, 8, 9, 12};

    // Test insert
    int[] b = insertAt(a, 2, 99);
    System.out.print("After insert: ");
    for (int x : b) System.out.print(x + " ");

    System.out.println();

    // Test delete
    deleteAt(b, 3);
    System.out.print("After delete: ");
    for (int x : b) System.out.print(x + " ");
  }
}

ลบด้วยอาร์เรย์ใหม่

public class Main {
  // Method to create a new array without the element at index k
  static int[] without(int[] a, int k) {
    // Validate index
    if (k < 0 || k >= a.length) {
      throw new IllegalArgumentException("bad index");
    }

    // New array has one fewer element
    int[] b = new int[a.length - 1];

    // Copy elements before k
    for (int p = 0; p < k; p = p + 1) {
      b[p] = a[p];
    }

    // Copy elements after k (shift left by one)
    for (int p = k + 1; p < a.length; p = p + 1) {
      b[p - 1] = a[p];
    }

    return b;
  }

  public static void main(String[] args) {
    int[] a = {5, 8, 9, 12, 15};

    // Remove element at index 2 (value = 9)
    int[] b = without(a, 2);

    // Print original
    System.out.print("Original array: ");
    for (int x : a) System.out.print(x + " ");
    System.out.println();

    // Print new array
    System.out.print("Array without index 2: ");
    for (int x : b) System.out.print(x + " ");
  }
}

สาธิตการแทรกและการลบ

public class Main {
  static int[] insertAt(int[] a, int i, int val) {
    if (i < 0 || i > a.length) throw new IllegalArgumentException("bad index");
    int[] b = new int[a.length + 1];
    for (int p = 0; p < i; p = p + 1) b[p] = a[p];
    b[i] = val;
    for (int p = i; p < a.length; p = p + 1) b[p + 1] = a[p];
    return b;
  }

  static void deleteAtShift(int[] a, int k) {
    if (k < 0 || k >= a.length) throw new IllegalArgumentException("bad index");
    for (int i = k; i < a.length - 1; i = i + 1) {
      a[i] = a[i + 1];
    }
    a[a.length - 1] = 0;
  }

  static int[] without(int[] a, int k) {
    if (k < 0 || k >= a.length) throw new IllegalArgumentException("bad index");
    int[] b = new int[a.length - 1];
    for (int p = 0; p < k; p = p + 1) b[p] = a[p];
    for (int p = k + 1; p < a.length; p = p + 1) b[p - 1] = a[p];
    return b;
  }

  static String join(int[] a) {
    String s = "";
    for (int i = 0; i < a.length; i = i + 1) {
      s = s + a[i] + (i + 1 < a.length ? " " : "");
    }
    return s;
  }

  public static void main(String[] args) {
    int[] a = {10, 20, 30, 40};
    System.out.println("a           = " + join(a));

    int[] b = insertAt(a, 2, 99);
    System.out.println("insertAt(2) = " + join(b));

    deleteAtShift(a, 1);
    System.out.println("deleteAt(1) = " + join(a));

    int[] c = without(b, 3);
    System.out.println("without(3)  = " + join(c));
  }
}

ตรวจสอบการลบและการเลื่อน

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