BFS和DFS

DFS

//C/C++
//递归写法：
map<int, int> visited;

void dfs(Node* root) {
  // terminator
  if (!root) return ;

  if (visited.count(root->val)) {
    // already visited
    return ;
  }

  visited[root->val] = 1;

  // process current node here. 
  // ...
  for (int i = 0; i < root->children.size(); ++i) {
    dfs(root->children[i]);
  }
  return ;
}

//C/C++
//非递归写法：
void dfs(Node* root) {
  map<int, int> visited;
  if(!root) return ;

  stack<Node*> stackNode;
  stackNode.push(root);

  while (!stackNode.empty()) {
    Node* node = stackNode.top();
    stackNode.pop();
    if (visited.count(node->val)) continue;
    visited[node->val] = 1;


    for (int i = node->children.size() - 1; i >= 0; --i) {
        stackNode.push(node->children[i]);
    }
  }

  return ;
}

BFS