题解 | #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) {
        queue<TreeNode*> Q;
        vector<int> output;
        if(root)
            Q.push(root);
        while(!Q.empty()) {
            TreeNode* t=Q.front();
            output.push_back(t->val);
            Q.pop();
            if(t->left)
                Q.push(t->left);
            if(t->right)
                Q.push(t->right);
        }
        return output;
    }
};