Union-Find with Compression

Union-find over fixed-size element sets: ``c void uf_init(int *parent, int *rank_, int n); int uf_find(int *parent, int x); void uf_union(int *parent, int *rank_, int a, int b); int uf_connected(int *parent, int a, int b); `` find uses path compression; union by rank; connected returns 1 iff same root.