How to determine whether a binary tree is complete?

Question

A complete binary tree is defined as a binary tree in which every level, except possibly the deepest, is completely filled. At deepest level, all nodes must be as far left a

Answer 1

For a tree to be complete

height(left) == height(right) or height(left) == 1+height(right)

    bool isComplete (struct Node* root){
    if(root==NULL)
    return true;                  // Recur for left and right subtree 
    bool flag=false;
    int option1=height(root->left);
    int option2=height(root->right);
    if(option1==option2||option1==option2+1)
    flag=true;
    return flag&&isComplete(root->left)&&isComplete(root->right);
    }