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Two Pointer

Linked List Cycle II (Find Entry)

**Problem Statement:** Given the required input arguments, write an efficient algorithm to solve the **Linked List Cycle II (Find Entry)** problem. Implement the required logic as specified by standard definitions for this classic algorithmic challenge. **Hint / Expected Approach:** Floyd's cycle detection + phase 2 pointer reset **Edge Cases to Consider:** - (1) No cycle - (2) Cycle at head - (3) Single node with self-loop

Examples

Example 1
Input: [3,2,0,-4], tail connects to index 1
Output: Node with value 2
Explanation: Basic cycle
Example 2
Input: [1,2], tail connects to index 0
Output: Node with value 1
Explanation: Cycle at head
Example 3
Input: [1], no cycle
Output: null
Explanation: Single node, no cycle

Constraints

  • ▪1 <= data.length <= 10^5
  • ▪Memory complexity must be O(1) or O(k)
  • ▪Ensure non-overlapping pointer access

Watch Out For Edge Cases

  • ▪No cycle
  • ▪Cycle at head
  • ▪Single node with self-loop
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