Code & Func

第69天。

Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

Example 1: Input:

1
1

/
0 2

L = 1 R = 2

Output:

Example 2: Input:

1
3

/
0 4
2 / 1

L = 1 R = 3

Output:

2 / 1

一开始没看到时二叉排序树，然后写的就有点复杂了：

1
TreeNode* trimBST(TreeNode* root, int L, int R) {
2
    if (!root) return nullptr;
3
    root->left = trimBST(root->left,L,R);
4
    root->right = trimBST(root->right,L,R);
5
    if (root->val >= L && root->val <= R) return root;
6
    else if (root->left != nullptr && root->right != nullptr) {
7
        auto p = root->left;
8
        while(p->left) p = p->left;
9
        p->left = root->right;
10
        return root->left;
11
    }
12
    return (root->left)?root->left:root->right;
13
}

1
TreeNode* trimBST(TreeNode* root, int L, int R) {
2
    if (root == nullptr) return nullptr;
3
    if (root->val < L) return trimBST(root->right,L,R);
4
    if (root->val > R) return trimBST(root->left,L,R);
5
    root->left = trimBST(root->left,L,R);
6
    root->right = trimBST(root->right,L,R);
7
    return root;
8
}