左神基础班 - 数一颗完全二叉树有多少个节点

逻辑，判断当前节点的右子树的最左下角节点是否到达最后一层，

若到达最后一层，则说明当前节点的左子树 是一颗，则用公式计算得到总数，然后 对当前节点的右子树 递归求解、

若当前节点的右子树 的最左下角节点没到最后一层，则当前 节点的 右子树是完全二叉树， 对左子树递归求解。

//当前节点的数，其左子树到最后一次了没？
int getHigh(TreeNode* node, int level){
	while(node != nullptr){
		level++;
		node = node->left;
	}
	return level -1;
}
int getCBTNum(TreeNode* head, int level, int total){
	if(level == total){
		return 1;
	}	
	if(getHigh(head->right,level+1) == total){
		return pow(2, total - level) + getCBTNum(head->right,level+1,total);
	}else{
		return pow(2, total - level -1) + getCBTNum(head->left,level+1,total);
	}
}
int nodeNum(TreeNode* head){
	if(head == nullptr){
		return 0;
	}
	return getCBTNum(head,1,getHigh(head,1));
}

 

总的代码：

#include
#include
#include
#include
using namespace std;
struct TreeNode{
	int value;
	TreeNode* left;
	TreeNode* right;
};
//当前节点的数，其左子树到最后一次了没？
int getHigh(TreeNode* node, int level){
	while(node != nullptr){
		level++;
		node = node->left;
	}
	return level -1;
}
int getCBTNum(TreeNode* head, int level, int total){
	if(level == total){
		return 1;
	}	
	if(getHigh(head->right,level+1) == total){
		return pow(2, total - level) + getCBTNum(head->right,level+1,total);
	}else{
		return pow(2, total - level -1) + getCBTNum(head->left,level+1,total);
	}
}
int nodeNum(TreeNode* head){
	if(head == nullptr){
		return 0;
	}
	return getCBTNum(head,1,getHigh(head,1));
}

string getTreeWithSerial(TreeNode* head){
	if(head == nullptr){
		return "#_";
	}
	char c[8];
	sprintf(c,"%d",head->value);
	string s = c;
	s = s+ '_';
	string s1 = getTreeWithSerial(head->left);
	string s2 = getTreeWithSerial(head->right);
	return s + s1 + s2;
}
TreeNode* getTree(int arr[],int length,int i){
	if(i < length){
		TreeNode* Treenode = new TreeNode();
		Treenode->value = arr[i];
		if((2*i+1) < length){
			Treenode->left = getTree(arr, length, 2*i+1);
		}else{
			Treenode->left = nullptr;
		}
		if((2*i+2)right = getTree(arr, length,2*i+2);
		}else{
			Treenode->right = nullptr;
		}
		return Treenode;
	}
	return nullptr;
}
int main(){
	int arr[] = {5,3,8,2,4,6,9,1};
	// int arr[] = {1,2};
	int length = sizeof(arr)/sizeof(arr[0]);
	//建树
	TreeNode* head = getTree(arr, length,0);
	//前序查看建树是否正确
	int num = nodeNum(head);
	// cout << "str : "<