Talk is cheap.

func hasSubtree(p1 *TreeNode, p2 *TreeNode) bool {
    if p1 == nil || p2 == nil {
        return false
    }
    if isPart(p1, p2) {
        return true
    }
    return hasSubtree(p1.Left, p2) || hasSubtree(p1.Right, p2)
}

func isPart(p1, p2 *TreeNode) bool {
    if p2 == nil {
        return true
    }
    if p1 == nil || p1.Val != p2.Val {
        return false
    }
    return isPart(p1.Left, p2.Left) && isPart(p1.Right, p2.Right)
}