feat : merge-k-sorted-list

Author: ekgns33

merge-k-sorted-lists/ekgns33.java

@@ -0,0 +1,86 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+  public ListNode mergeKLists(ListNode[] lists) {
+    List<ListNode> list = new LinkedList<>();
+    for(ListNode l : lists) {
+      list.add(l);
+    }
+    return divide(list);
+
+  }
+  public ListNode divide(List<ListNode> list) {
+    //두개씩 나누기. 두개 안되면 그냥 리스트에 넣고 리턴
+    int n = list.size();
+    ListNode sum1;
+    ListNode sum2;
+    if(list.size() <= 2) {
+      return merge(list);
+    }
+
+    int mid =  n / 2;
+    List<ListNode> upper = new LinkedList<>();
+    List<ListNode> last = new LinkedList<>();
+
+
+    for(int i = 0; i < mid; i ++) {
+      upper.add(list.get(i));
+
+    }
+    sum1 = divide(upper);
+
+
+    for(int i = mid; i < n; i++) {
+      last.add(list.get(i));
+    }
+    sum2 = divide(last);
+
+    List<ListNode> m = new LinkedList<>();
+    m.add(sum1);
+    m.add(sum2);
+
+
+    return merge(m);
+
+
+  }
+  public ListNode merge(List<ListNode> list) {
+    //edge
+    if(list.size()==0) return null;
+    if(list.size() == 1) return list.get(0);
+
+    ListNode n1 = list.get(0);
+    ListNode n2 = list.get(1);
+    // System.out.println(n1.val + " : " + n2.val);
+
+    ListNode res = new ListNode(0);
+    ListNode head = res;
+
+    while(n1 != null && n2 != null) {
+      if(n1.val < n2.val){
+        res.next = n1;
+        res = res.next;
+        n1 = n1.next;
+      } else {
+        res.next = n2;
+        res = res.next;
+        n2 = n2.next;
+      }
+
+    }
+    if(n1 == null) res.next = n2;
+    if(n2 == null) res.next = n1;
+    return head.next;
+
+
+
+  }
+}