int recursiveCountWithHeight(struct TreeNode* root,int height) {
if(NULL==root) return 0;
struct TreeNode *p=root;
int r_h=0;
while(NULL!=p) {
++r_h;
p=p->right;
}
if(height==r_h) {
return pow(2,height)-1;
} else {
return 1+recursiveCountWithHeight(root->left,height-1)
+recursiveCountWithHeight(root->right,height-1);
}
}
int countNodes(TreeNode* root) {
if(NULL==root) return 0;
TreeNode *p=root;
int height=0;
// left height only needs to be calculated once
while(NULL!=p){
++height;
p=p->left;
}
return recursiveCountWithHeight(root,height);
}
