intersection-of-two-linked-lists

intersection-of-two-linked-lists/sol.go

@@ -0,0 +1,29 @@
+package main
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+// O(n+m) time and O(n) memory solution
+// Only iterates over each list once, unlike
+// the other solution which iterates twice.
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func getIntersectionNode(headA, headB *ListNode) *ListNode {
+	exists := map[*ListNode]bool{}
+	for current := headA; current != nil; current = current.Next {
+		exists[current] = true
+	}
+	for current := headB; current != nil; current = current.Next {
+		if exists[current] {
+			return current
+		}
+	}
+	return nil
+}

intersection-of-two-linked-lists/sol_O(1)_mem.go

@@ -0,0 +1,43 @@
+package main
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+// O(n + m) time and O(1) memory solution
+// Gets the length of each list, then
+// lines them up and searches for equal
+// nodes.
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func getIntersectionNode(headA, headB *ListNode) *ListNode {
+	len1, len2 := getLen(headA), getLen(headB)
+	diff := len1 - len2
+	for diff > 0 {
+		headA = headA.Next
+		diff--
+	}
+	for diff < 0 {
+		headB = headB.Next
+		diff++
+	}
+	for headA != headB {
+		headA = headA.Next
+		headB = headB.Next
+	}
+	return headA
+}
+
+func getLen(head *ListNode) int {
+	len := 0
+	for current := head; current != nil; current = current.Next {
+		len++
+	}
+	return len
+}