[leetcode] 958. Check Completeness of a Binary Tree : https://leetcode.com/problems/check-completeness-of-a-binary-tree/

Check Completeness of a Binary Tree.cc

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    
    int cnt = 0;
    int maxInd = 0;
    
    void checkSubTree(TreeNode* root, int ind){
        if(root == NULL) return;
        cnt++;
        maxInd = max(maxInd, ind);
        checkSubTree(root->left, ind*2);
        checkSubTree(root->right, ind*2 + 1);
    }
    
    bool isCompleteTree(TreeNode* root) {
        checkSubTree(root, 1);
        return cnt == maxInd;
    }
};