AVL Tree - Left Rotate and Right Rotate (in LL, RR, LR and RL conditions)

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Hence Algorithm of left rotating a node in AVL tree :

treeNode leftRotate(cdn){
treeNode NR = cdn.right;
cdn.right = NR.left; // any left child of NR will be right child of cdn
NR.left = cdn;
// After doing rotation, we have to adjust the height of cdn and NR now
cdn.height = calculateHeight(cdn);
NR.height = calculateHeight(NR);

// finally we will return newRoot to the recursively calling function
return NR;
}


The algorithm of right rotate is just the mirror image of this :

treeNode rightRotate(cdn){
treeNode NR = cdn.left;
cdn.left= NR.right; // any right child of NR will be left child of cdn
NR.right= cdn;
// After doing rotation, we have to adjust the height of cdn and NR now
cdn.height = calculateHeight(cdn);
NR.height = calculateHeight(NR);

// finally we will return newRoot to the recursively calling function
return NR;
}

  • In LL condition, we do a rightRotate on cdn
  • In RR condition, we do a leftRotate on cdn
  • In RL condition, we do:
    • first, rightRotate on cdn.right
    • then, leftRotate on cdn
  • In LR condition, we do:
    • first, leftRotate on cdn.left
    • then, rightRotate on cdn

AVL tree is a special case of Binary Search tree in which we try to make a balanced tree by calculating the balance on each node and doing rotation based on LL, LR, RL and RR condtions in order to make the tree balanced.



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