【20230412】【每日一题】数组二叉树+最小叶子节点的路径

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

struct TreeNode {
	int val;
	TreeNode* left;
	TreeNode* right;
	TreeNode(int x) :val(x), left(nullptr), right(nullptr) {}
};
vector nums;

//构造二叉树
TreeNode* VecToTree(vector& nums,int startIndex,int n) {
	if (nums[startIndex] == -1)	return nullptr;//根结点为空
	TreeNode* root = new TreeNode(nums[startIndex]);
	//用根结点确定左右节点的位置
	int leftIndex = 2 * startIndex + 1;
	int rightIndex = 2 * startIndex + 2;
	if (leftIndex > n)	root->left = nullptr;
	else {
		root->left = VecToTree(nums, leftIndex, n);
	}
	if (rightIndex > n)	root->right = nullptr;
	else {
		root->right= VecToTree(nums, rightIndex, n);
	}
	return root;
}


//找最小叶子节点的路径

vector path;//记录到叶子节点的路径
vector result;//记录结果
int NowMin = INT_MAX;//动态维护当前找到最小节点的值
void backtracking(TreeNode* node, vector& path) {
	path.emplace_back(node->val);
	//如果到了叶子节点---终止条件
	if (node->left == nullptr && node->right == nullptr) {
		//此时path里已经装好了到叶子节点的路径
		int temp = path.back();
		if (temp < NowMin) {//当前这个路径的叶子节点更小
			result.clear();
			result = path;
			NowMin = temp;
		}
		return;
	}
	if (node->left) {
		backtracking(node->left, path);
		path.pop_back();
	}
	if (node->right) {
		backtracking(node->right, path);
		path.pop_back();
	}
}


int main() {
	string str;
	getline(cin, str);
	stringstream ss(str);
	string temp;
	while (getline(ss, temp, ' ')) {
		nums.emplace_back(stoi(temp));
	}
	TreeNode* root = VecToTree(nums,0,nums.size()-1);
	backtracking(root,path);
	for_each(result.begin(), result.end(), [=](int x) {cout << x << ' '; });
}