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| public class SortedArrayToBST {
public TreeNode sortedArrayToBST(int[] num) {
if (num.length < 1) {
return null;
}
if (num.length == 1) {
return new TreeNode(num[0]);
}
return helper(0, num.length - 1, num);
}
private TreeNode helper(int start, int end, int[] num) {
if (start <= end) {
int middle = (start + end) / 2;
TreeNode tree = new TreeNode(num[middle]);
tree.left = helper(start, middle - 1, num);
tree.right = helper(middle + 1, end, num);
return tree;
} else {
return null;
}
}
}
|