左叶子节点之和

#include <iostream>
#include <vector>
#include <stack>
#include <list>
#include <queue>
#include<string>

using namespace std;

typedef struct node
{
	int val;
	struct node* left;
	struct node* right;
}node_t;

using namespace std;

int leftNodeSum(node_t* root, bool isLeftNode)
{
	//如果当前节点是空节点，那么左叶子之和为0
	if (root == NULL)
	{
		return 0;
	}

	//如果当前节点不是空节点
	//判断当前节点是不是左叶子节点,如果是，返回这个节点的值
	if (isLeftNode && root->left == NULL && root->right == NULL)
	{
		return root->val;
	}

	//如果不是左叶子节点，就接着求该根节点的左子树和右子树的左叶子节点之和
	int left = leftNodeSum(root->left, true);
	int right = leftNodeSum(root->right, false);

	return left + right;


}

int main()
{
	node_t root;
	root.val = 1;

	node_t node2;
	node2.val = 2;

	node_t node3;
	node3.val = 3;

	node_t node4;
	node4.val = 4;

	node_t node5;
	node5.val = 5;

	node_t node6;
	node6.val = 6;

	node_t node7;
	node7.val = 7;

	node_t node8;
	node8.val = 8;


	root.left = &node2;
	root.right = &node3;

	node2.left = &node4;
	node2.right = &node5;

	node3.left = &node6;
	node3.right = NULL;

	node6.left = &node7;
	node6.right = NULL;

	node7.left = &node8;
	node7.right = NULL;

	node8.left = NULL;
	node8.right = NULL;

	node4.left = NULL;
	node4.right = NULL;

	node5.left = NULL;
	node5.right = NULL;


	int  sumRet = leftNodeSum(&root, false);

	cout << "sumRet_____________________________________" << sumRet << endl;
}