build binary tree

/* From Cracking the Coding Interview 4-3 */

/* Given a sorted (increasing order) array, write an algorithm to create a binary tree with minimal height. */

node * buildtree(int * n, int a, int b){
    if (b < a) {
        return nullptr;
    }

    int mid = (a + b) / 2;

    node * head = new node(n[mid]);

    head->left = buildtree(n, a, mid - 1);

    head->right = buildtree(n, mid + 1, b);

    return head;

}

void cleantree(node * n){

    if (n->left != nullptr)

        cleantree(n->left);

    if (n->right != nullptr)

        cleantree(n->right);

    delete n;

}