[LeetCode]108. Convert Sorted Array to Binary Search Tree

[LeetCode]108. Convert Sorted Array to Binary Search Tree

题目描述

思路

DFS
对于已经排好序的数组，构建二叉搜索树的时候可以按照索引构造，每次从当前序列的中点开始构造

代码

#include <iostream>
#include <vector>

using namespace std;

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return insert(nums, 0, nums.size());
    }

    TreeNode* insert(vector<int>& nums, int start, int end) {
        if (start >= end)
            return NULL;
        int cur = (end + start) >> 1;

        TreeNode* root = new TreeNode(nums[cur]);
        root->left = insert(nums, start, cur);
        root->right = insert(nums, cur + 1, end);
        return root;
    }
    void visit(TreeNode* root) {
        if (root == NULL)
            return;
        if (root->left) {
            visit(root->left);
        }
        cout << root->val << " ";
        if (root->right) {
            visit(root->right);
        }
    }
};

int main() {
    vector<int> nums = { 1, 2, 3,4,5 };
    Solution s;
    s.visit(s.sortedArrayToBST(nums));
    cout << endl;

    system("pause");
    return 0;
}