C/C++建一颗二叉树

在刷题的时候，很多时候给一个数组，需要建一个简单的二叉树

#include<iostream>
#include<vector>
#include<queue>

using namespace std;
struct TreeNode{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

TreeNode* newNode(int data){
    TreeNode* node = new TreeNode;
    node->val = data;
    node->left = node->right = nullptr;
    return node;
}

TreeNode* createTree(vector<int> &nums, int n, int index){
    TreeNode* node = nullptr;
    if (index < n && nums[index] != -1){
        node = newNode(nums[index]);
        node->left = createTree(nums, n, 2*index+1 );
        node->right = createTree(nums, n, 2*index+2 );
    }
    return node;
}

int main(){
    
    vector<int> nums{3,9,20,-1,-1,15,7};
    TreeNode* root = createTree(nums, nums.size(), 0);

    return 0;
}