力扣 题目99- 恢复二叉搜索树

题目

题解

在力扣 题目98- 验证二叉搜索树中 我们知道了 中序遍历后的二叉搜索树 应该为递增 那么出错就应该是有部分递减 那么我们在98题的基础上 反向检测 保存减少数列的开头与结尾进行交换

代码

#include<iostream>
#include<vector>
#include<stack>
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) {}
};
//遍历
//即减少序列的第一个数与最后一个数交换
class Solution {
public:
    void recoverTree(TreeNode* root) {
        TreeNode* last = new TreeNode(INT_MAX);
        TreeNode* max = new TreeNode(INT_MAX);
        TreeNode* min = new TreeNode(INT_MAX);
        stack<TreeNode*> ergodic;
        while (root != nullptr || !ergodic.empty()) {
            if (root != nullptr) {
                ergodic.push(root);
                root = root->left;
            }
            else
            {
                if (ergodic.top()->val < last->val) {
                    if (max->val == INT_MAX) {
                        max = last;
                    }
                    min = ergodic.top();
                }
                last = ergodic.top();
                root = ergodic.top()->right;
                ergodic.pop();
            }
        }
        swap(max->val, min->val);
    }

    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> result;
        stack<TreeNode*> ergodic;
        while (root != nullptr || !ergodic.empty()) {
            if (root != nullptr) {
                ergodic.push(root);
                root = root->left;
            }
            else
            {
                result.push_back(ergodic.top()->val);
                root = ergodic.top()->right;
                ergodic.pop();
            }
        }
        return result;
    }

};

int main() {
    Solution sol;
    TreeNode* head2 = new TreeNode(2);
    TreeNode* head3 = new TreeNode(3, nullptr, head2);
    TreeNode* head1 = new TreeNode(1, head3, nullptr);
    sol.recoverTree(head1);
    vector<int> resultforeach = sol.inorderTraversal(head1);
    for (int i = 0; i < resultforeach.size(); i++) {
        cout << resultforeach[i] << " ";
    }

}