力扣783 二叉搜索樹最小距離 前序遍歷

1、二叉搜索樹：左邊大於中間大於右邊

前序遍歷的遞歸代碼：

if(root==nullptr) return;

bfs(root->left);

res.push_back(root->val);

bfs()root->right);

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int>vec;
    void bfs(TreeNode* root)
    {
        if(root==nullptr)return;
        bfs(root->left);
        vec.push_back(root->val);
        bfs(root->right);
    }
    int minDiffInBST(TreeNode* root) {
        int mindiffer=INT_MAX;
        int diff=0;
        bfs(root);
        for(int i=0;i<vec.size()-1;i++)
        {
            diff=vec[i+1]-vec[i];
            if(diff<mindiffer) mindiffer=diff;
        }
        return mindiffer;
    }
};