平面图欧拉公式
- 对于一个连通平面图，记 \(F\) 为区域数， \(V\) 为点数，\(E\) 为边数，则有 \(F + V - E = 2\)
例题：
\(\texttt{ [THUPC2019]鸽鸽的分割}\)
\(\texttt{「USACO 2021.1 Platinum」Paint by Letters}\)
\(\texttt{[APIO2017]斑斓之地}\)
例题：
\(\texttt{ [THUPC2019]鸽鸽的分割}\)
\(\texttt{「USACO 2021.1 Platinum」Paint by Letters}\)
\(\texttt{[APIO2017]斑斓之地}\)