A snippet that can help you make TreeNode structure from Leetcode tree text like [1,2,-3,-5,null,4,null].

leetcode_tree.cpp

#include <algorithm>
#include <utility>
#include <stack>
#include <vector>
using namespace std;

#define null nullptr
struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};
struct _TreeNode {
	TreeNode *n;
	_TreeNode(nullptr_t): n(nullptr) {}
	_TreeNode(int i): n(new TreeNode(i)) {}
};

TreeNode* make_leetcode_tree(const std::vector<_TreeNode> &v)
{
	for (size_t i = 1; i < v.size(); i++) {
		if (v[i].n && v[(i-1)/2].n) {
			if (i%2 == 0)  v[(i-1)/2].n->right = v[i].n;
			else           v[(i-1)/2].n->left  = v[i].n;
		}
	}
	return v.front().n;
}

///////////////////////////
// Example: Leetcode 1080
///////////////////////////

class Solution {
	int cur_;
	int limit_;
	int Traverse(TreeNode *father, TreeNode *p) {
		cur_ += p->val;
		int max_val = 255<<24;
		if (p->left) {
			max_val = max(max_val, Traverse(p, p->left));
		}
		if (p->right) {
			max_val = max(max_val, Traverse(p, p->right));
		}
		int ret = p->val;
		if (p->left or p->right) {
			ret += max_val;
		}
		cur_ -= p->val;
		if (cur_ + ret < limit_ && father) {
			if (father->left == p) father->left = NULL;
			if (father->right == p) father->right = NULL;
		}
		return ret;
	}
	public:
	TreeNode* sufficientSubset(TreeNode* root, int limit) {
		TreeNode fake(0);
		limit_ = limit;
		fake.left = root;
		Traverse(nullptr, &fake);
		return fake.left;
	}
};

int main()
{
	Solution s;
	TreeNode *ans[] = {
		s.sufficientSubset(make_leetcode_tree({1,2,-3,-5,null,4,null}), -1),
		s.sufficientSubset(make_leetcode_tree({1,2,3,4,null,null,7,8,9,null,14}), 1),
		s.sufficientSubset(make_leetcode_tree({19116,-6419,-6972,-242,-942,11391,-3065,2811,-8816,-176,-3984,null,14568,18522,16054,null,-1050,-216,-3729,3064,-1069,9215,-3891,18451,null,10794,9707,3745,-8632,7591,11919,-1590,7734,5023,null,19776,-4844,6683,null,-8944,5188,null,11648,5969,null,null,null,null,null,18971,10446,385,-6543,null,15641,4466,-1091,null,null,null,9520,null,null,null,null,6182,103,3298,8811,10086,10004,-3613,13611,-7252,9553,null,null,null,11078,-6612,-551,null,null,6704,null,null,null,-7719,-6508,5648,3637,null,null,-6988,null,null,-7918,null,-4853,-3715,null,null,null,-8433,null,null,null,null,null,null,-4601,null,null,null,null,-2396,-5951,null,null,6509,9169,19019,11715,3478,null,5448,null,null,12673,null,null,null,null,null,5561,null,null,6088,null,null,17861,10581,18042,null,null,null,null,null,null,4163,15418,null,null,null,null,null,10111,null,-8427,null,12522,-1817,null,null,null,null,null,-1818,null,-579,7729,null,null,null,null,null,null,null,11712,2441,8892,null,null,null,null,7849,null,null,null,null,436,-7846,null,null,null,null,null,6982}), 801432710)
	};
	return 0;
}