Maximum distance between any two nodes of a Binary Tree (a.k.a Diameter or Width of the Tree)

Question: Given a binary tree, write a program to find maximum distance between any two nodes of the tree.

Time Complexity: O(n)

int

diameter(tree *t)
{
    /* left diamter, right diameter, node diameter */
    int ld, rd, nd;

    if (!t) {
        return 0;
    }

    ld = diameter(t->left);
    rd = diameter(t->right);
    nd  = height(t->left) + height(t->right) + 1;

    return max3(ld, rd, nd);
}

Slightly more efficient algorithm, this calculates the height of the tree along with diameter.

int
diameter2(tree *t, int *height)
{
    /* left diameter, right diameter, node diameter */
    int ld, rd, nd;

    /* left height, right height */
    int lh, rh;

    if (!t) {
        *height = 0;
        return 0;
    }

    ld = diameter2(t->left, &lh);
    rd = diameter2(t->right, &rh);
    nd  = lh + rh + 1;

    *height = max(lh, rh) + 1;
    return max3(ld, rd, nd);

}

max3 - returns maximum of the three arguments