[learning notes] graph theory thinking problem

chain reaction （chain）

• Everything can be constructed fool around with
• Obviously, it can be considered in connected blocks
• If this connected block can be divided into two sets without edges inside $X$,$Y$, And only exist $X\to Y$ The edge of , Then obviously, new edges cannot be generated
• If I can construct three sets without edges inside $X$,$Y$,$Z$, And only exist $X\to Y$,$Y\to Z$,$Z\to X$ The edge of , So clearly $X,Y,Z$ Will maintain internal independence , And the final number of sides is $|X||Y|+|Y||Z|+|X||Z|$
• If I can't construct it, then this connected block is a complete graph
• For convenience , Can be constructed in the context of an undirected graph
• Complexity $O(n+m)$