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701. Insert into a Binary Search Tree
Given the root node of a binary search tree (BST) and a value to be inserted into the tree, insert the value into the BST. Return the root node of the BST after the insertion. It is guaranteed that the new value does not exist in the original BST.
Note that there may exist multiple valid ways for the insertion, as long as the tree remains a BST after insertion. You can return any of them.
For example,
Given the tree:
4
/ \
2 7
/ \
1 3
And the value to insert: 5You can return this binary search tree:
4
/ \
2 7
/ \ /
1 3 5This tree is also valid:
5
/ \
2 7
/ \
1 3
\
4思路分析
二叉搜索树的特性：左中右是有序的。如果插入的值比当前节点小，那么就在左子树上找，如果最节点为空，直接插入；否则就不断 cur = cur.left。如果插入的值更大，亦是如此。
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/**
* @author D瓜哥 · https://www.diguage.com
* @since 2024-06-26 19:33:15
*/
public TreeNode insertIntoBST(TreeNode root, int val) {
if (root == null) {
return new TreeNode(val);
}
TreeNode curr = root;
while (curr != null) {
if (val < curr.val) {
if (curr.left == null) {
curr.left = new TreeNode(val);
break;
} else {
curr = curr.left;
}
} else {
if (curr.right == null) {
curr.right = new TreeNode(val);
break;
} else {
curr = curr.right;
}
}
}
return root;
}