Finding the common ancestor in a binary tree

Question

This question was asked to me in an interview: I have a binary tree and I have to find the common ancestor (parent) given two random nodes of that tree. I am also given a point

Answer 1

@Above, this will not work, because you are assuming that both nodes are immediate child of some particular node...

            8
     10           12
 7             

and I gave the nodes as 7 and 12, answer must be 8. Lets do like this

    find(root, d1, d2, n1=null, n2=null)
     {
          if(n1 && n2) return;
          if(!root) return;

          else  if(root -> d == d1 ) n1 = root;
          else  if(root -> d == d2 ) n2 = root;                     
          find(root->left, d1, d2, n1, n2);
          find(root->right, d1, d2, n1, n2);
     }

     LCA(root, d1, d2)
     {
         node *n1=null, *n2=null;
         find(root, d1, d2, n1, n2);
         if(n1 == null || n2 == null )error 'nodes not present' exit(0);
         findIntersect(n1, n2); 
     }
     findInterSect(node *n1, node *n2)
     {
        l1 = length(n1);
        l2 = length(n2);
        node *g = n2, *l = n1;
        diff = abs(l1 - l2);
        if(l1>l2) g = n1 l =n2 
        while(diff) g = g->parent; diff--;
        // now both nodes are at same level
        while(g != l) g= g->parent, l = l->parent;
     }