2.7. intersection v2

02. Linked lists/2.7. intersection.java

@@ -0,0 +1,44 @@
+public static LinkedListNode intersect(LinkedListNode a, LinkedListNode b){
+
+    if (a == null || b == null) return null;
+
+    LinkedListNode a_head = a;
+    LinkedListNode b_head = b;
+    int a_len, b_len = 1;
+
+    // iterate through A
+    while (a_head.next != null){
+        a_head = a_head.next;
+        a_len += 1;
+    }
+
+    // iterate through B
+    while (b_head.next != null){
+        b_head = b_head.next;
+        b_len += 1;
+    }
+
+    // last node inequal, return null
+    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;
+
+    // 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){
+        longer = longer.next;
+        k--;
+    }
+
+    // there's intersection
+    while(shorter != longer){
+        shorter = shorter.next;
+        longer = longer.next;
+    }
+
+    return shorter;
+}

02. Linked lists/2.7. intersection.md

@@ -249,54 +249,4 @@ Takeaways:
 * When comparing nodes, compare `a == b`, not `a.data == b.data`
 * Get a new class for the tail and lengths
 
-Improved algorithm:
+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`.
-
-```java
-
-public static LinkedListNode intersect(LinkedListNode a, LinkedListNode b){
-
-    if (a == null || b == null) return null;
-
-    LinkedListNode a_head = a;
-    LinkedListNode b_head = b;
-    int a_len, b_len = 1;
-
-    // iterate through A
-    while (a_head.next != null){
-        a_head = a_head.next;
-        a_len += 1;
-    }
-
-    // iterate through B
-    while (b_head.next != null){
-        b_head = b_head.next;
-        b_len += 1;
-    }
-
-    // last node inequal, return null
-    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;
-
-    // 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){
-        longer = longer.next;
-        k--;
-    }
-
-    // there's intersection
-    while(shorter != longer){
-        shorter = shorter.next;
-        longer = longer.next;
-    }
-
-    return shorter;
-}
-```
-
-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`.