99. 恢复二叉搜索树

int midOrder(struct TreeNode **pre, struct TreeNode **err1, struct TreeNode **err2, struct TreeNode *root)
{
    if (root == NULL) return 0;
    
    if (midOrder(pre, err1, err2, root->left) == -1) return -1;
    if (*pre != NULL && (*pre)->val > root->val) {
        if (*err1 == NULL) {
            *err1 = *pre;
            *err2 = root;
        } else {
            *err2 = root;
            return -1;
        }
    }
    *pre = root;
    if (midOrder(pre, err1, err2, root->right) == -1) return -1;
    return 0;
}

void recoverTree(struct TreeNode* root){
    struct TreeNode *pre = NULL;
    struct TreeNode * err1 = NULL;
    struct TreeNode * err2 = NULL;
    midOrder(&pre, &err1, &err2, root);
    
    int tmp;
    tmp = err1->val;
    err1->val = err2->val;
    err2->val = tmp;
    return;
}


作者：liqiang64
链接：https://leetcode-cn.com/problems/recover-binary-search-tree/solution/cyu-yan-zhong-xu-bian-li-yi-bian-ji-ke-kong-jian-f/
来源：力扣（LeetCode）
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