Check whether a given binary tree is perfect or not
Given a Binary Tree, write a function to check whether the given Binary Tree is a perfect Binary Tree or not.
A Binary tree is Perfect Binary Tree in which all internal nodes have two children and all leaves are at same level.
Examples:
The following tree is a perfect binary tree
10 / \ 20 30 / \ / \ 40 50 60 70 18 / \ 15 30
The following tree is not a perfect binary tree
1 / \ 2 3 \ / \ 4 5 6
A Perfect Binary Tree of height h (where height is number of nodes on path from root to leaf) has 2h – 1 nodes.
Below is an idea to check whether a given Binary Tree is perfect or not.
- Find depth of any node (in below tree we find depth of leftmost node). Let this depth be d.
- Now recursively traverse the tree and check for following two conditions.
- Every internal node should have both children non-empty
- All leaves are at depth ‘d’
C++
// C++ program to check whether a given // Binary Tree is Perfect or not #include<bits/stdc++.h> /* Tree node structure */ struct Node { int key; struct Node *left, *right; }; // Returns depth of leftmost leaf. int findADepth(Node *node) { int d = 0; while (node != NULL) { d++; node = node->left; } return d; } /* This function tests if a binary tree is perfect or not. It basically checks for two things : 1) All leaves are at same level 2) All internal nodes have two children */ bool isPerfectRec( struct Node* root, int d, int level = 0) { // An empty tree is perfect if (root == NULL) return true ; // If leaf node, then its depth must be same as // depth of all other leaves. if (root->left == NULL && root->right == NULL) return (d == level+1); // If internal node and one child is empty if (root->left == NULL || root->right == NULL) return false ; // Left and right subtrees must be perfect. return isPerfectRec(root->left, d, level+1) && isPerfectRec(root->right, d, level+1); } // Wrapper over isPerfectRec() bool isPerfect(Node *root) { int d = findADepth(root); return isPerfectRec(root, d); } /* Helper function that allocates a new node with the given key and NULL left and right pointer. */ struct Node *newNode( int k) { struct Node *node = new Node; node->key = k; node->right = node->left = NULL; return node; } // Driver Program int main() { struct Node* root = NULL; root = newNode(10); root->left = newNode(20); root->right = newNode(30); root->left->left = newNode(40); root->left->right = newNode(50); root->right->left = newNode(60); root->right->right = newNode(70); if (isPerfect(root)) printf ( "Yes\n" ); else printf ( "No\n" ); return (0); } |
Java
// Java program to check whether a given // Binary Tree is Perfect or not class GfG { /* Tree node structure */ static class Node { int key; Node left, right; } // Returns depth of leftmost leaf. static int findADepth(Node node) { int d = 0 ; while (node != null ) { d++; node = node.left; } return d; } /* This function tests if a binary tree is perfect or not. It basically checks for two things : 1) All leaves are at same level 2) All internal nodes have two children */ static boolean isPerfectRec(Node root, int d, int level) { // An empty tree is perfect if (root == null ) return true ; // If leaf node, then its depth must be same as // depth of all other leaves. if (root.left == null && root.right == null ) return (d == level+ 1 ); // If internal node and one child is empty if (root.left == null || root.right == null ) return false ; // Left and right subtrees must be perfect. return isPerfectRec(root.left, d, level+ 1 ) && isPerfectRec(root.right, d, level+ 1 ); } // Wrapper over isPerfectRec() static boolean isPerfect(Node root) { int d = findADepth(root); return isPerfectRec(root, d, 0 ); } /* Helper function that allocates a new node with the given key and NULL left and right pointer. */ static Node newNode( int k) { Node node = new Node(); node.key = k; node.right = null ; node.left = null ; return node; } // Driver Program public static void main(String args[]) { Node root = null ; root = newNode( 10 ); root.left = newNode( 20 ); root.right = newNode( 30 ); root.left.left = newNode( 40 ); root.left.right = newNode( 50 ); root.right.left = newNode( 60 ); root.right.right = newNode( 70 ); if (isPerfect(root) == true ) System.out.println( "Yes" ); else System.out.println( "No" ); } } |
Python3
# Python3 program to check whether a # given Binary Tree is Perfect or not # Helper class that allocates a new # node with the given key and None # left and right pointer. class newNode: def __init__( self , k): self .key = k self .right = self .left = None # Returns depth of leftmost leaf. def findADepth(node): d = 0 while (node ! = None ): d + = 1 node = node.left return d # This function tests if a binary tree # is perfect or not. It basically checks # for two things : # 1) All leaves are at same level # 2) All internal nodes have two children def isPerfectRec(root, d, level = 0 ): # An empty tree is perfect if (root = = None ): return True # If leaf node, then its depth must # be same as depth of all other leaves. if (root.left = = None and root.right = = None ): return (d = = level + 1 ) # If internal node and one child is empty if (root.left = = None or root.right = = None ): return False # Left and right subtrees must be perfect. return (isPerfectRec(root.left, d, level + 1 ) and isPerfectRec(root.right, d, level + 1 )) # Wrapper over isPerfectRec() def isPerfect(root): d = findADepth(root) return isPerfectRec(root, d) # Driver Code if __name__ = = '__main__' : root = None root = newNode( 10 ) root.left = newNode( 20 ) root.right = newNode( 30 ) root.left.left = newNode( 40 ) root.left.right = newNode( 50 ) root.right.left = newNode( 60 ) root.right.right = newNode( 70 ) if (isPerfect(root)): print ( "Yes" ) else : print ( "No" ) # This code is contributed by pranchalK |
C#
// C# program to check whether a given // Binary Tree is Perfect or not using System; class GfG { /* Tree node structure */ class Node { public int key; public Node left, right; } // Returns depth of leftmost leaf. static int findADepth(Node node) { int d = 0; while (node != null ) { d++; node = node.left; } return d; } /* This function tests if a binary tree is perfect or not. It basically checks for two things : 1) All leaves are at same level 2) All internal nodes have two children */ static bool isPerfectRec(Node root, int d, int level) { // An empty tree is perfect if (root == null ) return true ; // If leaf node, then its depth must be same as // depth of all other leaves. if (root.left == null && root.right == null ) return (d == level+1); // If internal node and one child is empty if (root.left == null || root.right == null ) return false ; // Left and right subtrees must be perfect. return isPerfectRec(root.left, d, level+1) && isPerfectRec(root.right, d, level+1); } // Wrapper over isPerfectRec() static bool isPerfect(Node root) { int d = findADepth(root); return isPerfectRec(root, d, 0); } /* Helper function that allocates a new node with the given key and NULL left and right pointer. */ static Node newNode( int k) { Node node = new Node(); node.key = k; node.right = null ; node.left = null ; return node; } // Driver code public static void Main() { Node root = null ; root = newNode(10); root.left = newNode(20); root.right = newNode(30); root.left.left = newNode(40); root.left.right = newNode(50); root.right.left = newNode(60); root.right.right = newNode(70); if (isPerfect(root) == true ) Console.WriteLine( "Yes" ); else Console.WriteLine( "No" ); } } /* This code is contributed by Rajput-Ji*/ |
Javascript
<script> // Javascript program to check whether a given // Binary Tree is Perfect or not /* Tree node structure */ class Node { constructor() { this .key = 0; this .left = null ; this .right = null ; } } // Returns depth of leftmost leaf. function findADepth(node) { var d = 0; while (node != null ) { d++; node = node.left; } return d; } /* This function tests if a binary tree is perfect or not. It basically checks for two things : 1) All leaves are at same level 2) All internal nodes have two children */ function isPerfectRec(root, d, level) { // An empty tree is perfect if (root == null ) return true ; // If leaf node, then its depth must be same as // depth of all other leaves. if (root.left == null && root.right == null ) return (d == level + 1); // If internal node and one child is empty if (root.left == null || root.right == null ) return false ; // Left and right subtrees must be perfect. return isPerfectRec(root.left, d, level + 1) && isPerfectRec(root.right, d, level + 1); } // Wrapper over isPerfectRec() function isPerfect(root) { var d = findADepth(root); return isPerfectRec(root, d, 0); } /* Helper function that allocates a new node with the given key and NULL left and right pointer. */ function newNode(k) { var node = new Node(); node.key = k; node.right = null ; node.left = null ; return node; } // Driver code var root = null ; root = newNode(10); root.left = newNode(20); root.right = newNode(30); root.left.left = newNode(40); root.left.right = newNode(50); root.right.left = newNode(60); root.right.right = newNode(70); if (isPerfect(root) == true ) document.write( "Yes" ); else document.write( "No" ); // This code is contributed by noob2000 </script> |
Output:
Yes
Time complexity: O(n)
Method 2: Using the length of the binary tree
Since a full binary tree has 2^h – 1 nodes, we can count the number of nodes in the binary tree and determine whether it is a power of 2 or not.
To efficiently determine whether it is a power of 2 or not, we can use bitwise operation x & (x+1) == 0
Python3
# Python3 program to check whether a # given Binary Tree is Perfect or not # Helper class that allocates a new # node with the given key and None # left and right pointer. class newNode: def __init__( self , k): self .key = k self .right = self .left = None #This functions gets the size of binary tree #Basically, the number of nodes this binary tree has def getLength(root): if root = = None : return 0 return 1 + getLength(root.left) + getLength(root.right) #Returns True if length of binary tree is a power of 2 else False def isPerfect(root): length = getLength(root) return length & (length + 1 ) = = 0 # Driver Code if __name__ = = '__main__' : root = None root = newNode( 10 ) root.left = newNode( 20 ) root.right = newNode( 30 ) root.left.left = newNode( 40 ) root.left.right = newNode( 50 ) root.right.left = newNode( 60 ) root.right.right = newNode( 70 ) if (isPerfect(root)): print ( "Yes" ) else : print ( "No" ) # This code is contributed by beardedowl |
Javascript
<script> // JavaScript program to check whether a // given Binary Tree is Perfect or not // Helper class that allocates a new // node with the given key and None // left and right pointer. class newNode{ constructor(k){ this .key = k this .right = this .left = null } } // This functions gets the size of binary tree // Basically, the number of nodes this binary tree has function getLength(root){ if (root == null ) return 0 return 1 + getLength(root.left) + getLength(root.right) } // Returns True if length of binary tree is a power of 2 else False function isPerfect(root){ let length = getLength(root) return length & (length+1) == 0 } // Driver Code let root = null root = new newNode(10) root.left = new newNode(20) root.right = new newNode(30) root.left.left = new newNode(40) root.left.right = new newNode(50) root.right.left = new newNode(60) root.right.right = new newNode(70) if (isPerfect(root)) document.write( "Yes" ) else document.write( "No" ) // This code is contributed by shinjanpatra </script> |
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