Should we use array or linked list for storing tree data structure

Not all trees are created using arrays. Whether a tree is stored in an array or linked nodes depends on the type of tree and the operations you need. Let me explain clearly.

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1️⃣ Complete Binary Trees / Heaps → Array

• Examples: Min-Heap, Max-Heap, Binary Heap
• Reason: They are complete binary trees (all levels full except possibly last).
• Storage: Contiguous array works well because children and parent indices can be calculated easily:

Index i:
Left child  = 2*i + 1
Right child = 2*i + 2
Parent      = (i-1)/2

✅ Advantages:

• Memory-efficient
• Fast index-based access
• No extra pointers

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2️⃣ General Binary Trees → Linked Nodes

• Examples: BST, AVL, Red-Black Tree
• Reason: Trees may be sparse or unbalanced, so using an array wastes space.
• Storage: Each node has:

struct Node {
    int data;
    Node* left;
    Node* right;
};

✅ Advantages:

• Flexible size, no need for contiguous memory
• Works for any tree shape
• Can easily add/remove nodes dynamically

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3️⃣ Summary Table

Tree Type	Storage Method	Why
Complete Binary Tree / Heap	Array	Easy index math, contiguous memory
Sparse or Unbalanced Tree	Linked Nodes	Avoid wasted space, flexible shape
Binary Search Tree (BST)	Linked Nodes	Dynamic insertion/deletion
Trie / N-ary Tree	Linked nodes / pointers	Each node can have variable number of children

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Key Takeaway

• Use array: Only for complete or almost complete binary trees (heaps, segment trees).
• Use linked nodes: For general trees, sparse trees, or when tree shape is dynamic.

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