题目描述:
从上到下按层打印二叉树,同一层结点从左至右输出。每一层输出一行。
思路:
对二叉树广搜,打印当前节点的时候,先把其子节点加入到队尾。用两个变量分别表示当前层还未打印节点数量和下层节点数量控制每层一行输出。
代码:
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :val(x), left(NULL), right(NULL) {
}
};
class Solution {
public:
vector<vector<int> > Print(TreeNode* pRoot) {
if (pRoot == NULL) return {};
queue<TreeNode*> que;
que.push(pRoot);
int curlevel = 1;
int nxtlevel = 0;
vector<vector<int> >ans;
vector<int> temp;
while(!que.empty()) {
TreeNode* cur = que.front();
que.pop();
temp.push_back(cur->val);
curlevel--;
if (cur->left != NULL) {
que.push(cur->left);
nxtlevel++;
}
if (cur->right != NULL) {
que.push(cur->right);
nxtlevel++;
}
if (curlevel == 0) {
curlevel = nxtlevel;
nxtlevel = 0;
ans.push_back(temp);
temp.clear();
}
}
return ans;
}
};
碌碌无为的一天又过去了。