CodingInterview-从上往下打印二叉树

二叉树的层序遍历，使用队列即可。

/*
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(root==NULL) return result;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            TreeNode* n=q.front();
            q.pop();
            result.push_back(n->val);
            if(n->left!=NULL) q.push(n->left);
            if(n->right!=NULL) q.push(n->right);
        }
        return result;
    }
};