题解 | #求二叉树的层序遍历#

/**
 * struct TreeNode {
 *  int val;
 *  struct TreeNode *left;
 *  struct TreeNode *right;
 *  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param root TreeNode类
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > levelOrder(TreeNode* root) {
        // write code here
        if (root == nullptr) {
            return m_retVal;
        }
        queue<TreeNode*> qu;
        qu.push(root);
        while (!qu.empty()) {
            vector<int> tempVec;
            int size = qu.size();
            for (int i = 0; i < size; ++i) {
                TreeNode* tempNode = qu.front();
                tempVec.push_back(tempNode->val);
                qu.pop();
                if (tempNode->left != nullptr) {
                    qu.push(tempNode->left);
                }
                if (tempNode->right != nullptr) {
                    qu.push(tempNode->right);
                }
            }
            m_retVal.push_back(tempVec);
        }
        return m_retVal;
    }
  private:
    vector<vector<int>> m_retVal;
};