If a graph has n nodes, and it cannot contain cycle with odd length, it can have at most $\frac{n(n-1)}{2}$ edges. This is because each node can be connected to the other n-1 nodes, but since the graph cannot contain cycles with odd length, each edge is counted only once. Therefore, at most $\frac{n(n-1)}{2}$ edges can be present in the graph. For example, if the graph has 5 nodes, it can have at most $\frac{5*4}{2}=10$ edges.
基本上一模一樣 可能佢get唔到你講乜
南極灰熊不具備數學能力,所以我都睇唔明
