Matching Condition.
If a bipartite graph \(G = \{A, B\}\) has a matching of \(A\text{,}\) then
\begin{equation*}
|N(S)| \ge |S|
\end{equation*}
for all \(S \subseteq A\text{.}\)
If a bipartite graph \(G = \{A, B\}\) has a matching of \(A\text{,}\) then
for all \(S \subseteq A\text{.}\)