Lookup()

Given a binary search tree and a "target" value, search the tree to see if it contains the target. The basic pattern of
the lookup() code occurs in many recursive tree algorithms: deal with the base case where the tree is empty, deal
with the current node, and then use recursion to deal with the subtrees. If the tree is a binary search tree, there is
often some sort of less-than test on the node to decide if the recursion should go left or right.
/*
Given a binary tree, return true if a node
with the target data is found in the tree. Recurs
down the tree, chooses the left or right
branch by comparing the target to each node.
*/
static int lookup(struct node* node, int target) {
// 1. Base case == empty tree
// in that case, the target is not found so return false
if (node == NULL) {
return(false);
}
else {
// 2. see if found here
if (target == node->data) return(true);
else {
// 3. otherwise recur down the correct subtree
if (target < node->data) return(lookup(node->left, target));
else return(lookup(node->right, target));
}
}
}