C++ Program to Find Deepest Left Leaf in a Binary Tree

A binary tree which has at most two children, specified as left child and right child. This is a C++ Program to Find Deepest Left Leaf in a Binary Tree

Algorithm

Begin.
   function deepestLLeafutil() find the deepest left leaf in a given
   binary tree:  
      lvel is level of current node.
      maxlvel is pointer to the deepest left leaf node found so far  
      isLeft Indicates that this node is left child of its parent  
      resPtr is Pointer to the result  
      If root is equal to Null then  
         Return.  
      Update result if this node is having a left leaf and its level is
      more than the max level of the current result.  
      Recursively call function deepestLLeafutil() for left and right subtrees. 
End.

Example Code

 Live Demo

#include <iostream>
using namespace std;
struct n {
   int v;
   n *l, *r;
};
void deepestLLeafutil(n *root, int lvel, int *maxvel, bool isLeft, n **resPtr) {
   if (root == NULL)
      return;
   if (isLeft && !root->l && !root->r && lvel > *maxvel) {
      *resPtr = root;
      *maxvel = lvel;
      return;
   }
   deepestLLeafutil(root->l, lvel + 1, maxvel, true, resPtr);
   deepestLLeafutil(root->r, lvel + 1, maxvel, false, resPtr);
}
n* deepestLLeaf( n *root) {
   int maxlevel = 0;
   n *res = NULL;
   deepestLLeafutil(root, 0, &maxlevel, false, &res);
   return res;
}
n *newnode(int d) {
   n *t = new n;
   t->v = d;
   t->l = t->r = NULL;
   return t;
}
int main() {
   n* root = newnode(9);
   root->l = newnode(7);
   root->r = newnode(10);
   root->l->l = newnode(6);
   root->r->l= newnode(8);
   root->r->r = newnode(19);
   root->r->l->r = newnode(4);
   root->r->r->r = newnode(20);
   n *res = deepestLLeaf(root);
   if (res)
      cout << "The deepest left leaf is " << res->v;
   else
      cout << "There is no left leaf in the given tree";
   return 0;
}

Output

The deepest left leaf is 6