给你一个多叉树。移出所有子树，当这个子树的全部节点的值的和为０。

struct TreeNode {

vector children;

int val;

TreeNode(int v) : val(v) {};

~TreeNode() { for (TreeNode* cnode: children) delete cnode; }

};

int subtree_sum(TreeNode* &pnode) {

if (pnode == nullptr) return 0;. visit 1point3acres.com for more.

int sum = pnode->val;

for (TreeNode* cnode : pnode->children) sum += subtree_sum(cnode);

if (sum == 0) {

delete pnode;-google 1point3acres

pnode = NULL;. 

}

return sum;

}