### Sum of Leaf nodes of a tree

Problem-Given a binary tree.Our task is to find the sum of all leaf nodes.
Approach-Problem can be easily solved by using DFS traversal of a tree.

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#include<bits/stdc++.h> using namespace std; struct Node{ int data; Node* left; Node* right; }; int sumLeaf(Node* root) { if(root==NULL) { return 0; } if(root->left==NULL && root->right ==NULL) { return root->data; } return (sumLeaf(root->left)+sumLeaf(root->right)); } struct Node* buildTree(int* preorder,int* inorder,int inorder_start,int inorder_end,int preorder_start,int preorder_end){ if(inorder_start>inorder_end){ return NULL; } int search=preorder[preorder_start]; int index=-1; for(int y=inorder_start;y<=inorder_end;y++){ if(inorder[y]==search){ index=y; break; } } int left_inorder_start=inorder_start; int left_inorder_end=index-1; int left_preOrder_start=preorder_start+1; int left_preOrder_end = (left_inorder_end-left_inorder_start)+left_preOrder_start; int right_inorder_start=index+1; int right_inorder_end=inorder_end; int right_preOrder_start=left_preOrder_end+1; int right_preOrder_end=preorder_end; struct Node* root = (struct Node*)malloc(sizeof(struct Node)); root->data=preorder[preorder_start]; root->left=buildTree(preorder,inorder,left_inorder_start,left_inorder_end,left_preOrder_start,left_preOrder_end); root->right=buildTree(preorder,inorder,right_inorder_start,right_inorder_end,right_preOrder_start,right_preOrder_end); return root; } int main(){ cout<<"Enter the size of the Tree "<<endl; int siz; cin>>siz; int in[siz]; int pre[siz]; cout<<"Enter the Inorder Traversal of the Tree "<<endl; for(int y=0;y< siz ;y++){ cin>>in[y]; } cout<<"Enetr the PreOrder traversal of thre Tree "<<endl; for(int h =0;h<siz;h++){ cin>>pre[h]; } struct Node* r=buildTree(pre,in,0,(siz-1),0,(siz-1)); //The r is the root int sum=sumLeaf(r); cout<<sum; return ; }
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