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.

Basic Implementation

Basic.java 
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));
    }
}

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