给定一棵二叉树，求所有叶节点的和。 例如：
null
Input : 1 / 2 3 / / 4 5 6 7 8Output :Sum = 4 + 5 + 8 + 7 = 24
其思想是以任何方式遍历树，并检查该节点是否为叶节点。如果节点是叶节点，则将节点数据添加到sum变量。 以下是上述方法的实现。
C++
// CPP program to find sum of // all leaf nodes of binary tree #include<bits/stdc++.h> using namespace std; // struct binary tree node struct Node{ int data; Node *left, *right; }; // return new node Node *newNode( int data){ Node *temp = new Node(); temp->data = data; temp->left = temp->right = NULL; return temp; } // utility function which calculates // sum of all leaf nodes void leafSum(Node *root, int & sum){ if (!root) return ; // add root data to sum if // root is a leaf node if (!root->left && !root->right) sum += root->data; // propagate recursively in left // and right subtree leafSum(root->left, sum); leafSum(root->right, sum); } // driver program int main(){ //construct binary tree Node *root = newNode(1); root->left = newNode(2); root->left->left = newNode(4); root->left->right = newNode(5); root->right = newNode(3); root->right->right = newNode(7); root->right->left = newNode(6); root->right->left->right = newNode(8); // variable to store sum of leaf nodes int sum = 0; leafSum(root, sum); cout << sum << endl; return 0; } |
JAVA
// Java program to find sum of // all leaf nodes of binary tree public class GFG { // user define class node static class Node{ int data; Node left, right; // constructor Node( int data){ this .data = data; left = null ; right = null ; } } static int sum; // utility function which calculates // sum of all leaf nodes static void leafSum(Node root){ if (root == null ) return ; // add root data to sum if // root is a leaf node if (root.left == null && root.right == null ) sum += root.data; // propagate recursively in left // and right subtree leafSum(root.left); leafSum(root.right); } // driver program public static void main(String args[]) { //construct binary tree Node root = new Node( 1 ); root.left = new Node( 2 ); root.left.left = new Node( 4 ); root.left.right = new Node( 5 ); root.right = new Node( 3 ); root.right.right = new Node( 7 ); root.right.left = new Node( 6 ); root.right.left.right = new Node( 8 ); // variable to store sum of leaf nodes sum = 0 ; leafSum(root); System.out.println(sum); } } // This code is contributed by Sumit Ghosh |
Python3
# Python3 Program to find the #sum of leaf nodes of a binary tree # Class for node creation class Node: # Constructor def __init__( self , data): self .data = data self .left = None self .right = None # Utility function to calculate # the sum of all leaf nodes def leafSum(root): global total if root is None : return if (root.left is None and root.right is None ): total + = root.data leafSum(root.left) leafSum(root.right) # Binary tree Fromation if __name__ = = '__main__' : root = Node( 1 ) root.left = Node( 2 ) root.left.left = Node( 4 ) root.left.right = Node( 5 ) root.right = Node( 3 ) root.right.right = Node( 7 ) root.right.left = Node( 6 ) root.right.left.right = Node( 8 ) # Variable to store the sum of leaf nodes total = 0 leafSum(root) # Printing the calculated sum print (total) # This code is contributed by Naren Sai Krishna |
C#
using System; // C# program to find sum of // all leaf nodes of binary tree public class GFG { // user define class node public class Node { public int data; public Node left, right; // constructor public Node( int data) { this .data = data; left = null ; right = null ; } } public static int sum; // utility function which calculates // sum of all leaf nodes public static void leafSum(Node root) { if (root == null ) { return ; } // add root data to sum if // root is a leaf node if (root.left == null && root.right == null ) { sum += root.data; } // propagate recursively in left // and right subtree leafSum(root.left); leafSum(root.right); } // driver program public static void Main( string [] args) { //construct binary tree Node root = new Node(1); root.left = new Node(2); root.left.left = new Node(4); root.left.right = new Node(5); root.right = new Node(3); root.right.right = new Node(7); root.right.left = new Node(6); root.right.left.right = new Node(8); // variable to store sum of leaf nodes sum = 0; leafSum(root); Console.WriteLine(sum); } } // This code is contributed by Shrikant13 |
Javascript
<script> // Javascript program to find sum of // all leaf nodes of binary tree // user define class node class Node { constructor(data) { this .left = null ; this .right = null ; this .data = data; } } let sum; // utility function which calculates // sum of all leaf nodes function leafSum(root){ if (root == null ) return ; // add root data to sum if // root is a leaf node if (root.left == null && root.right == null ) sum += root.data; // propagate recursively in left // and right subtree leafSum(root.left); leafSum(root.right); } // construct binary tree let root = new Node(1); root.left = new Node(2); root.left.left = new Node(4); root.left.right = new Node(5); root.right = new Node(3); root.right.right = new Node(7); root.right.left = new Node(6); root.right.left.right = new Node(8); // variable to store sum of leaf nodes sum = 0; leafSum(root); document.write(sum); // This code is contributed by divyesh072019. </script> |
输出：
24
时间复杂性： O（n）
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