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 Bash 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.sh
Replay: real traced execution (multi-file project)
#!/usr/bin/env bash
set -euo pipefail

render() {
  local idx="$1"
  local out=""
  while [[ "$idx" != "-1" ]]; do
    if [[ -n "$out" ]]; then out+=" -> "; fi
    out+="${value[$idx]}"
    idx="${next[$idx]}"
  done
  printf '%s -> null\n' "$out"
}

declare -A value
declare -A next
value[1]=10; next[1]=2
value[2]=20; next[2]=3
value[3]=30; next[3]=4
value[4]=40; next[4]=-1
head=1
target=30
cursor="$head"
while [[ "${next[$cursor]}" != "-1" ]]; do
  candidate="${next[$cursor]}"
  if [[ "${value[$candidate]}" == "$target" ]]; then
    next[$cursor]="${next[$candidate]}"
    break
  fi
  cursor="$candidate"
done
render "$head"

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

    1#!/usr/bin/env bash2set -euo pipefail
    values this step10 -> 20 -> 30 -> 40 -> nullhead30target

  2. cursor ← node(20)

    6local out=""7while [[ "$idx" != "-1" ]]; do8  if [[ -n "$out" ]]; then out+=" -> "; fi
    values this stepnode(10) → node(20)cursor

  3. cursor.next ← node(40)

    1#!/usr/bin/env bash2set -euo pipefail
    values this stepnode(30) → node(40)cursor.next

  4. stdout ← 10 -> 20 -> 40 -> null

    11  done12  printf '%s -> null\n' "$out"13}
    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.