Linked Structures

Delete by Value

Find the node before the target value and rewire its next pointer so the target node leaves the chain.

Algorithm

The replay labels nodes by value, such as node(20), and never exposes object identity or memory addresses. This Java DSA implementation uses the same small chain as the rest of the DSA track.

predecessor Deletion needs the node before the one being removed.
rewiring The predecessor skips the target and points at the target's next node.

Basic Implementation

Basic.java
Replay: real traced execution (multi-file project)
public class Basic {
    static class Node {
        int value;
        Node next;
        Node(int value) { this.value = value; }
        Node(int value, Node next) { this.value = value; this.next = next; }
    }
    static String render(Node head) {
        StringBuilder out = new StringBuilder();
        Node cursor = head;
        while (cursor != null) {
            if (out.length() > 0) out.append(" -> ");
            out.append(cursor.value);
            cursor = cursor.next;
        }
        return out.append(" -> null").toString();
    }
    public static void main(String[] args) {
        Node head = new Node(10, new Node(20, new Node(30, new Node(40))));
        int target = 30;
        Node cursor = head;
        while (cursor.next != null) {
            if (cursor.next.value == target) {
                cursor.next = cursor.next.next;
                break;
            }
            cursor = cursor.next;
        }
        System.out.println(render(head));
    }
}

  1. head ← 10 -> 20 -> 30 -> 40 -> null, target ← 30

    1public class Basic {2    static class Node {
    values this step10 -> 20 -> 30 -> 40 -> nullhead30target

  2. cursor ← node(20)

    10Node cursor = head;11while (cursor != null) {12    if (out.length() > 0) out.append(" -> ");
    values this stepnode(10) → node(20)cursor

  3. cursor.next ← node(40)

    23if (cursor.next.value == target) {24    cursor.next = cursor.next.next;25    break;
    values this stepnode(30) → node(40)cursor.next

  4. stdout ← 10 -> 20 -> 40 -> null

    28    }29    System.out.println(render(head));30}
    values this step10 -> 20 -> 40 -> nullstdout10 -> 20 -> 40 -> nullhead

Complexity

  • Time: O(n)
  • Space: O(1)

Implementation notes

  • Keep the explicit node and pointer/reference operations; array shortcuts hide the linked-list state this lesson is meant to replay.
  • The final output prints the chain in a deterministic a -> b -> null form for cross-language comparison.