liinked list

Author: genkimaru

src/main/java/com/leetcode/linkedlist/IntersectTwoList.java

@@ -0,0 +1,72 @@
+package com.leetcode.linkedlist;
+
+import com.leetcode.util.ListNode;
+import com.leetcode.util.Utils;
+
+import java.util.HashSet;
+
+/**
+ *  name:  two intersect list
+ */
+public class IntersectTwoList {
+
+    //use hashset to store the node
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        HashSet<ListNode> set = new HashSet<>() ;
+        ListNode curNodeA = headA;
+        int lenA = 0;
+        while(curNodeA.next != null){
+            set.add(curNodeA);
+            lenA ++;
+            curNodeA = curNodeA.next;
+        }
+        ListNode curNodeB = headB;
+        int lenB = 0;
+        while(curNodeB.next != null){
+            boolean b = set.add(curNodeB);
+            if(!b){
+                return curNodeB;
+            }
+            lenB ++;
+            curNodeB = curNodeB.next;
+
+        }
+        return null;
+    }
+
+    public static void main(String[] args) {
+
+        // build linked list
+        //  [4,1,8,4,5]
+        ListNode node1 = new ListNode(4);
+        ListNode node2 = new ListNode(1);
+        ListNode node3 = new ListNode(8);
+        ListNode node4 = new ListNode(5);
+        node1.next = node2;
+        node2.next = node3;
+        node3.next = node4;
+
+        //    [5,6,1,8,4,5]
+        ListNode node11 = new ListNode(5);
+        ListNode node22 = new ListNode(6);
+        ListNode node33 = new ListNode(1);
+        //   ListNode node44 = new ListNode(8);
+        ListNode node55 = new ListNode(4);
+        ListNode node66 = new ListNode(5);
+
+        node11.next = node22;
+        node22.next = node33;
+        node33.next = node3;
+        node3.next = node55;
+        node55.next = node66;
+
+
+        ListNode intersectionNode =  new IntersectTwoList().getIntersectionNode(node1, node11);
+        if (intersectionNode != null) {
+            System.out.println(intersectionNode.val);
+        } else {
+            System.out.println("null");
+        }
+    }
+
+}

src/main/java/com/leetcode/linkedlist/IntersectTwoListS.java

@@ -0,0 +1,79 @@
+package com.leetcode.linkedlist;
+
+import com.leetcode.util.ListNode;
+
+public class IntersectTwoListS {
+
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        ListNode curA = headA;
+        ListNode curB = headB;
+        int lenA = 0, lenB = 0;
+        while (curA != null) { // 求链表A的长度
+            lenA++;
+            curA = curA.next;
+        }
+        while (curB != null) { // 求链表B的长度
+            lenB++;
+            curB = curB.next;
+        }
+        curA = headA;
+        curB = headB;
+        // 让curA为最长链表的头，lenA为其长度
+        if (lenB > lenA) {
+            //1. swap (lenA, lenB);
+            int tmpLen = lenA;
+            lenA = lenB;
+            lenB = tmpLen;
+            //2. swap (curA, curB);
+            ListNode tmpNode = curA;
+            curA = curB;
+            curB = tmpNode;
+        }
+        // 求长度差
+        int gap = lenA - lenB;
+        // 让curA和curB在同一起点上（末尾位置对齐）
+        while (gap-- > 0) {
+            curA = curA.next;
+        }
+        // 遍历curA 和 curB，遇到相同则直接返回
+        while (curA != null) {
+            if (curA == curB) {
+                return curA;
+            }
+            curA = curA.next;
+            curB = curB.next;
+        }
+        return null;
+    }
+
+
+    public static void main(String[] args) {
+        // build linked list
+        //  [4,1,8,4,5]
+        ListNode node1 = new ListNode(4);
+        ListNode node2 = new ListNode(1);
+        ListNode node3 = new ListNode(8);
+        ListNode node4 = new ListNode(5);
+        node1.next = node2;
+        node2.next = node3;
+        node3.next = node4;
+
+        //    [5,6,1,8,4,5]
+        ListNode node11 = new ListNode(5);
+        ListNode node22 = new ListNode(6);
+        ListNode node33 = new ListNode(1);
+        //   ListNode node44 = new ListNode(8);
+        ListNode node55 = new ListNode(4);
+        ListNode node66 = new ListNode(5);
+
+        node11.next = node22;
+        node22.next = node33;
+        node33.next = node3;
+        node3.next = node55;
+        node55.next = node66;
+
+        ListNode intersectionNode = new IntersectTwoListS().getIntersectionNode(node1, node11);
+        System.out.println(intersectionNode.val);
+
+    }
+}

src/main/java/com/leetcode/linkedlist/LinkedListOne.java

@@ -10,46 +10,6 @@
  */
 public class LinkedListTwo {
 
-/*    public ListNode mergeTwoLists(ListNode head1, ListNode head2) {
-        ListNode newHead, currentNode;
-        ListNode currentHead1 = head1, currentHead2 = head2;
-        if (head1.val < head2.val) {
-            newHead = head1;
-            currentNode = newHead;
-            currentHead1 = head1.next;
-
-        } else if (head1.val > head2.val) {
-            newHead = head2;
-            currentNode = newHead;
-            currentHead2 = head2.next;
-        } else {
-            currentHead1 = head1.next;
-            currentHead2 = head2.next;
-            newHead = head1;
-            newHead.next = head2;
-            currentNode = newHead.next;
-
-        }
-        while (currentHead1 != null && currentHead2 != null) {
-            if (currentHead1.val < currentHead2.val || currentHead2 == null) {
-                currentNode.next = currentHead1;
-                currentHead1 = currentHead1.next;
-
-            } else if (currentHead1.val > currentHead2.val || currentHead1 == null) {
-                currentNode.next = currentHead2;
-                currentHead2 = currentHead2.next;
-            } else {
-                currentHead1 = currentHead1.next;
-                currentHead2 = currentHead2.next;
-                currentNode.next = currentHead1;
-                currentNode.next.next = currentHead2;
-
-            }
-        }
-
-        return newHead;
-    }*/
-
     public ListNode mergeTwoLists(ListNode head1, ListNode head2) {
         ArrayList<Integer>  list = new ArrayList<Integer>();
         while(head1 != null && head2 != null){