Free a Graph Exactly Once

The boilerplate declares a tiny DAG of named nodes: ``c typedef struct GNode { char name; struct GNode **kids; /* array of borrowed pointers, kids_len long */ size_t kids_len; } GNode; ` kids and its pointers are **owned by the node**; a node may be a child of several parents (shared, borrowed from the parents' view). Implement: `c /* frees every distinct node reachable from root exactly once, then the kids arrays, then returns how many nodes were freed */ size_t graph_free(GNode *root); ``

Difficulty: intermediate