[LeetCode] 445. 两数相加 II
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自己想的太复杂了。。。。。
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { ListNode pre=null; ListNode head=null; ListNode l1node=l1,l2node=l2; pre.next=head; int l1len=0; int l2len=0; whille(l1node!=null){ l1len++; l1node=l1node.next; } whille(l2node!=null){ l2len++; l2node=l2node.next; } if(l1len>l2len){ int m=l1len-l2len; while(m!=0){ head=l1; pre=head; head=head.next; l1=l1.next; m--; } }else{ int m=l2len-l1len; while(m!=0){ head=l1; pre=head; head=head.next; l2=l2.next; m--; } } while(l1!=null){ int c1=l1==null?0:c1.val; int c2=l2==null?0:c2.val; int sum=(c1+c2)%10; int carry=(c1+c2)/10; if(carry==1) pre+=1; head=sum; pre=sum; head=head.next; } } }
然而可以用栈放进去,出来就是数字从低位到高位了。
class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { Stack<Integer> stack1 = new Stack<>(); Stack<Integer> stack2 = new Stack<>(); while (l1 != null) { stack1.push(l1.val); l1 = l1.next; } while (l2 != null) { stack2.push(l2.val); l2 = l2.next; } int carry = 0; ListNode head = null; while (!stack1.isEmpty() || !stack2.isEmpty() || carry > 0) { int sum = carry; sum += stack1.isEmpty()? 0: stack1.pop(); sum += stack2.isEmpty()? 0: stack2.pop(); ListNode node = new ListNode(sum % 10); node.next = head; head = node; carry = sum / 10; } return head; } }
或者是直接翻转链表,然后按照第2题那样的方法去做更快
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { ListNode dummyHead = new ListNode(0); ListNode p = reverseList(l1); ListNode q = reverseList(l2); ListNode cur = dummyHead; int carry = 0; while (p != null || q != null){ int x = (p != null) ? p.val : 0; int y = (q != null) ? q.val : 0; int sum = x + y + carry; carry = sum/10; cur.next = new ListNode(sum%10); cur = cur.next; if (p != null){ p = p.next; } if (q != null){ q = q.next; } } if (carry == 1){ cur.next = new ListNode(carry); } return reverseList(dummyHead.next); } public static ListNode reverseList(ListNode cur) { ListNode pre = null; while (cur != null) { ListNode temp = cur.next; cur.next = pre; pre = cur; cur = temp; } return pre; } }
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