题解 | #判断是不是完全二叉树#

/**
 * struct TreeNode {
 *  int val;
 *  struct TreeNode *left;
 *  struct TreeNode *right;
 *  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <iterator>
#include <queue>
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 bool布尔型
     */
    bool isCompleteTree(TreeNode* root) {
        // write code here
        queue<TreeNode*> fatherNodes, childNodes;
        fatherNodes.push(root);
        bool flag = false; // 是否遇到空的节点？
        while (!fatherNodes.empty()) {
            if (fatherNodes.front()->left != nullptr) {
                if (flag) {
                    return false;
                }
                childNodes.push(fatherNodes.front()->left);
            } else {
                flag = true;
            }
           
            if (fatherNodes.front()->right != nullptr) {
                if (flag) {
                    return false;
                }
                childNodes.push(fatherNodes.front()->right);
            } else {
                flag = true;
            }
            fatherNodes.pop();
            if (fatherNodes.empty()) {
                while (!childNodes.empty()) {
                    fatherNodes.push(childNodes.front());
                    childNodes.pop();
                }
            }
        }
        return true;
    }
};