萤火虫-N2

Author: yasinshaw

src/main/java/N1_100/N2.java

@@ -0,0 +1,55 @@
+package N1_100;
+
+import common.ListNode;
+
+public class N2 {
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        // 先加起来，不处理进位
+        ListNode result = addIgnoreCarry(l1, l2);
+        carry(result);
+        return result;
+    }
+
+    // 直接相加，忽略进位
+    private ListNode addIgnoreCarry(ListNode l1, ListNode l2) {
+        ListNode head = new ListNode(l1.val + l2.val);
+        ListNode result = head;
+        l1 = l1.next;
+        l2 = l2.next;
+        while (l1 != null && l2 != null) {
+            head.next = new ListNode(l1.val + l2.val);
+            l1 = l1.next;
+            l2 = l2.next;
+            head = head.next;
+        }
+        if (l1 != null) {
+            head.next = l1;
+        } else if (l2 != null) {
+            head.next = l2;
+        }
+        return result;
+    }
+
+    // 处理进位
+    private void carry(ListNode listNode) {
+        boolean needCarry = false; // 当前是否需要进位
+        while (listNode != null) {
+            int val = listNode.val;
+            if (needCarry) {
+                val += 1;
+            }
+            if (val >= 10) {
+                listNode.val = val % 10;
+                needCarry = true;
+                if (listNode.next == null) {
+                    listNode.next = new ListNode(1);
+                    break;
+                }
+            } else {
+                listNode.val = val;
+                needCarry = false;
+            }
+            listNode = listNode.next;
+        }
+    }
+}