/**
* Initializes a new digraph that is a deep copy of the specified digraph. 拷贝构造
*
* @param G the digraph to copy
*/
public Digraph(Digraph G) {
this(G.V());
this.E = G.E();
for (int v = 0; v < V; v++) this.indegree[v] = G.indegree(v);
for (int v = 0; v < G.V(); v++) {
// reverse so that adjacency list is in same order as original
// 保证原序
Stack<Integer> reverse = new Stack<Integer>();
for (int w : G.adj[v]) {
reverse.push(w);
}
for (int w : reverse) {
adj[v].add(w);
}
}
}
