1+ // Check if a binary tree is subtree of another binary tree
2+ // Root of the source tree and the tree to be matched are provided in the parameters.
3+ // Return true/false based on whether or not the given tree is the subtree of the source tree
4+ // Time complexity : O(m*n) m is the number of nodes of the original tree,
5+ // n is the number of nodes in the tree to be matched
6+ 7+ function areIdentical ( rootOfOriginalTree , rootOfMatchingTree ) {
8+ if ( rootOfOriginalTree === null && rootOfMatchingTree === null ) {
9+ return true ;
10+ }
11+ 12+ if ( rootOfOriginalTree === null || rootOfMatchingTree === null ) {
13+ return false ;
14+ }
15+ 16+ return ( rootOfOriginalTree . value === rootOfMatchingTree . value ) && areIdentical ( rootOfOriginalTree . leftChild , rootOfMatchingTree . leftChild ) && areIdentical ( rootOfOriginalTree . rightChild , rootOfMatchingTree . rightChild ) ;
17+ }
18+ 19+ function isSubtree ( rootOfOriginalTree , rootOfMatchingTree ) {
20+ if ( rootOfMatchingTree === null ) {
21+ return true ;
22+ }
23+ 24+ if ( rootOfOriginalTree === null ) {
25+ return false ;
26+ }
27+ 28+ if ( areIdentical ( rootOfOriginalTree , rootOfMatchingTree ) ) {
29+ return true ;
30+ }
31+ 32+ return isSubtree ( rootOfOriginalTree . leftChild , rootOfMatchingTree ) || isSubtree ( rootOfMatchingTree . rightChild , rootOfMatchingTree ) ;
33+ }
34+ 35+ module . exports = {
36+ isSubtree,
37+ } ;
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