C++: Print tree to a dot/graphviz graph. Derive from this class and generate graph of a tree or a node hierarchy of your choice and save it to a .dot file.

GraphPrinter.h

#pragma once
#include <sstream>
#include <fstream>
#include <string>

// Inherit from this class, passing your node type as T
// template argument. Override GetNumChildren, GetChildNode
// and GetNodeName to provide a way of accessing node's name,
// its children and number of them.
template<typename T>
class AbstractGraphPrinter
{
public:
    void WriteDot(const T* node, const char* filename)
    {
        std::stringstream ss;
        ss << "digraph G {" << std::endl;
        WriteRecursively(node, ss);
        ss << "}" << std::endl;
        std::ofstream file;
        file.open(filename);
        file << ss.rdbuf();
        file.close();
    }
    virtual ~AbstractGraphPrinter() {};
protected:
    // Returns number of node's children
    virtual size_t GetNumChildren(const T* parent) = 0;
    // Retrieves the ith child from a parent
    virtual const T* GetChildNode(const T* parent, size_t child_id) = 0;
    // Returns node's name, which will appear on the graph
    virtual std::string GetNodeName(const T* node) = 0;
private:
    void WriteRecursively(const T* node, std::stringstream& ss)
    {
        size_t children_num = GetNumChildren(node);
        for(unsigned i = 0; i < children_num; i++)
        {
            const T* child = GetChildNode(node, i);
            ss << "\"" << GetNodeName(node) << "\" -> \"" << GetNodeName(child) << "\"" << std::endl;
            WriteRecursively(child, ss);
        }
    }
};

WorkingExample.cpp

#include "GraphPrinter.h"

struct Node
{
  std::string name;
  Node* children;
  size_t children_num;
};

class NodeGraphPrinter : public AbstractGraphPrinter<Node>
{
private:
    size_t GetNumChildren(const Node* parent) final
    {
        return (size_t)parent->children_num;
    }

    const Node* GetChildNode(const Node* parent, size_t child_id) final
    {
        return &parent->children[child_id];
    }

    std::string GetNodeName(const Node* node) final
    {
        return node->name;
    }
};

int main()
{
  Node* root = GenerateTree(); // defined somewhere else
  NodeGraphPrinter printer;
  printer.WriteDot(root, "file.dot");
  return 0;
}