From f789821c88ff09ce88f1eb115e53671493cea9a7 Mon Sep 17 00:00:00 2001
From: AndyLiuLei <61106135+AndyLiuLei@users.noreply.github.com>
Date: Sun, 16 Feb 2020 16:01:39 +0800
Subject: [PATCH] Update BTree.java

need to update the key of the firstchild of the node while insert and return a new node
---
 src/main/java/edu/princeton/cs/algs4/BTree.java | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/main/java/edu/princeton/cs/algs4/BTree.java b/src/main/java/edu/princeton/cs/algs4/BTree.java
index 35183e845..e052ff313 100644
--- a/src/main/java/edu/princeton/cs/algs4/BTree.java
+++ b/src/main/java/edu/princeton/cs/algs4/BTree.java
@@ -181,7 +181,15 @@ private Node insert(Node h, Key key, Value val, int ht) {
         else {
             for (j = 0; j < h.m; j++) {
                 if ((j+1 == h.m) || less(key, h.children[j+1].key)) {
+                    int k = j ;
                     Node u = insert(h.children[j++].next, key, val, ht-1);
+                    
+                    // update key
+                    Node nextNode = h.children[k].next ;
+                    if (null != nextNode ) {
+                   	    h.children[k].key = nextNode.children[0].key ;
+                    }
+                    
                     if (u == null) return null;
                     t.key = u.children[0].key;
                     t.next = u;