From 13e1e805a627c44623f5e12dd941837c3f533af7 Mon Sep 17 00:00:00 2001
From: anebz <ane.berasategi@gmail.com>
Date: Fri, 9 Aug 2019 00:03:49 +0200
Subject: [PATCH] Updated exercises and README with ch2

---
 02. Linked lists/2.7. intersection.java | 33 ++++++++++++++++++++++---
 02. Linked lists/2.7. intersection.md   |  4 +++
 README.md                               |  5 ++++
 3 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/02. Linked lists/2.7. intersection.java b/02. Linked lists/2.7. intersection.java
index 274695f..67383dd 100644
--- a/02. Linked lists/2.7. intersection.java	
+++ b/02. Linked lists/2.7. intersection.java	
@@ -4,7 +4,8 @@ public static LinkedListNode intersect(LinkedListNode a, LinkedListNode b){
 
     LinkedListNode a_head = a;
     LinkedListNode b_head = b;
-    int a_len, b_len = 1;
+    int a_len = 1;
+    int b_len = 1;
 
     // iterate through A
     while (a_head.next != null){
@@ -22,16 +23,16 @@ public static LinkedListNode intersect(LinkedListNode a, LinkedListNode b){
     if (a_head != b_head) return null; // changed from before
 
     // compare lengths, adjust node
-    if (a_len == 1 or b_len == 1) return a_head;
+    if (a_len == 1 || b_len == 1) return a_head;
 
     // improved
     LinkedListNode shorter = a_len < b_len ? a : b;
     LinkedListNode longer = b_len < a_len ? b : a;
     int diff = Math.abs(a_len - b_len);
 
-    while(k > 0 && longer != null){
+    while(diff > 0 && longer != null){
         longer = longer.next;
-        k--;
+        diff--;
     }
 
     // there's intersection
@@ -41,4 +42,28 @@ public static LinkedListNode intersect(LinkedListNode a, LinkedListNode b){
     }
 
     return shorter;
+}
+
+// https://stackoverflow.com/questions/1594061/check-if-two-linked-lists-merge-if-so-where/14956113#14956113
+static int FindMergeNode(LinkedListNode headA, LinkedListNode headB) {
+    LinkedListNode currentA = headA;
+    LinkedListNode currentB = headB;
+
+    // Do till the two nodes are the same
+    while (currentA != currentB) {
+        // If you reached the end of one list start at the beginning of the other one
+        // currentA
+        if (currentA.next == null) {
+            currentA = headB;
+        } else {
+            currentA = currentA.next;
+        }
+        // currentB
+        if (currentB.next == null) {
+            currentB = headA;
+        } else {
+            currentB = currentB.next;
+        }
+    }
+    return currentB.data;
 }
\ No newline at end of file
diff --git a/02. Linked lists/2.7. intersection.md b/02. Linked lists/2.7. intersection.md
index 2d0451b..ccf285a 100644
--- a/02. Linked lists/2.7. intersection.md	
+++ b/02. Linked lists/2.7. intersection.md	
@@ -250,3 +250,7 @@ Takeaways:
 * Get a new class for the tail and lengths
 
 Improved algorithm in **2.7. intersection.java**. Because we're comparing by reference not value, the condition in `while` won't be met if two nodes have the same `.data` but different `.next`.
+
+## Update
+
+New solution found [at stackoverflow](https://stackoverflow.com/questions/1594061/check-if-two-linked-lists-merge-if-so-where/14956113#14956113), without any pointers.
diff --git a/README.md b/README.md
index 0654013..2765989 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,11 @@
 * Partition list
 * Sum lists
 * Check if palindrome
+* List intersection
+* Loop detection
+* Insert node at beginning
+* Insert node at end
+* Reverse list, single and double linked
 
 ## Chapter 7 Object-oriented design