每日一题 剑指offer（从上往下打印二叉树）

struct TreeNode {
  int val;
  struct TreeNode *left;
  struct TreeNode *right;
  TreeNode(int x) :
      val(x), left(NULL), right(NULL) {
  }
};

class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        vector<int> result;
        if(NULL == root)
            return result;
        queue<TreeNode* > q;
        q.push(root);
        while(!q.empty())
        {
            TreeNode* temp = q.front();
            q.pop();
            result.push_back(temp->val);
            if(NULL != temp->left)
                q.push(temp->left);
            if(NULL != temp->right)
                q.push(temp->right);
        }
        return result;
    }
};