题解 | #求二叉树的层序遍历#思路就是建一个队列存下每层所有的结点，再把结点的值存入vector里
求二叉树的层序遍历
http://www.nowcoder.com/practice/04a5560e43e24e9db4595865dc9c63a3
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
class Solution {
public:
/**
*
* @param root TreeNode类
* @return int整型vector<vector<>>
*/
vector<vector<int> > levelOrder(TreeNode* root) {
vector<vector<int>> v;
vector<int> a;
queue<TreeNode*> q;
q.push(root);
int n;
TreeNode* t;
if(root == nullptr){
return v;
}
while(!q.empty()){
a.clear();
n = q.size();
for(int i = 0;i < n;i++){
t = q.front();
a.push_back(t->val);
q.pop();
if(t->left){
q.push(t->left);
}
if(t->right){
q.push(t->right);
}
}
v.push_back(a);
}
return v;
}
};
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