leetcode 589. N叉树的前序遍历

递归

class Solution {
public:
    vector<int> ret;
    vector<int> preorder(Node* root) {
        findw(root);
        return ret;
    }
    void findw(Node*root){
        if( root!= nullptr ){
            ret.push_back( root->val );
            for( auto i:root->children ){
                findw( i );
            }
        }
    }
};