I have seen many time people starting dfs with starting node -1 but I don't understand why do they do this.Can you please tell me why do they do so like in this example.
# | User | Rating |
---|---|---|
1 | tourist | 4009 |
2 | jiangly | 3839 |
3 | Radewoosh | 3646 |
4 | jqdai0815 | 3620 |
4 | Benq | 3620 |
6 | orzdevinwang | 3612 |
7 | Geothermal | 3569 |
8 | ecnerwala | 3494 |
9 | Um_nik | 3396 |
10 | gamegame | 3386 |
# | User | Contrib. |
---|---|---|
1 | Um_nik | 164 |
2 | -is-this-fft- | 160 |
2 | maomao90 | 160 |
4 | atcoder_official | 158 |
4 | cry | 158 |
4 | awoo | 158 |
7 | adamant | 155 |
8 | nor | 154 |
9 | TheScrasse | 153 |
10 | Dominater069 | 152 |
Name |
---|
It's not starting point, it's a parent of verticle in DFS's spannig tree. There is no parent of root of the spanning tree, so it's equal to -1