private TreeNode buildTree(
int[] inorder, int inStart, int inEnd, int[] postorder, int postStart, int postEnd) {
// base case
if (inStart > inEnd) {
return null;
}
if (inStart == inEnd) {
return new TreeNode(inorder[inStart]);
}
// recursive case
int rootVal = postorder[postEnd];
// find root value in inorder array
int rootIndexInInorder = -1;
for (int i = inStart; i <= inEnd; i++) {
if (inorder[i] == rootVal) {
rootIndexInInorder = i;
break;
}
}
TreeNode root = new TreeNode(rootVal);
int leftEnd = rootIndexInInorder - 1 - inStart + postStart;
root.left = buildTree(inorder, inStart, rootIndexInInorder - 1, postorder, postStart, leftEnd);
root.right =
buildTree(inorder, rootIndexInInorder + 1, inEnd, postorder, leftEnd + 1, postEnd - 1);
return root;
}
// 3
// \
// 20
// /
// 15
@Test
public void Test3() {
TreeNode t1 = new TreeNode(3);
TreeNode t3 = new TreeNode(20);
TreeNode t4 = new TreeNode(15);
TreeNode.connect(t1, null, t3);
TreeNode.connect(t3, t4, null);
TreeNode root = t1;
List<List<Integer>> actual = solution.levelOrder(root);
List<List<Integer>> expected = new ArrayList<>();
expected.add(Arrays.asList(3));
expected.add(Arrays.asList(20));
expected.add(Arrays.asList(15));
assertEquals(expected, actual);
}