0133-clone-graph.ts

letdfs=(node: Node,memo: Map<Node,Node>)=>{
if(node===null)returnnull;

//if this node has already been visited, simply return the counterpart node of the new graph and return
if(memo.has(node))returnmemo.get(node);

//node hasn't been already visited, create its counterpart version for the new graph
letnewNode=newNode(node.val);
//maps to the old graph counterpart(also marked as visited)
memo.set(node,newNode);

//for each edge of the old node, add that edge in the new graph node
for(leti=0;i<node.neighbors.length;i++){
newNode.neighbors.push(dfs(node.neighbors[i],memo));
}

returnnewNode;
};

functioncloneGraph(node: Node|null): Node|null{
//uses a map, maps old graph nodes with new graph ones
//it also tells us which node of the old graph have already been visited
letmemo=newMap<Node,Node>();

returndfs(node,memo);
}