标签：self most 出现 public ini ext git red for
Given a non-negative integer represented as non-empty a singly linked list of digits, plus one to the integer.
You may assume the integer do not contain any leading zero, except the number 0 itself.
The digits are stored such that the most significant digit is at the head of the list.
Example:
Input: 1->2->3 Output: 1->2->4
和+1数组有点像，关键要知道最多只要记录一串X9999就够了，前面的都是浮云，如果出现小于9的数字就相当于屏障，再也影响不到它之前的了。
最后这串被记录下来的，每个digit都做 digit = (digit + 1) % 10的操作。如果最前面的X也是9，那说明其实你整串肯定都是9999999，否则如89999不可能会最后存下来的第一个是9的。这个时候特殊还要再加一个1在最前头。
关于怎么记录有两种方法：
1.O(n) 空间：用一个stack。存下来后一个个吐回去
2.O(1)空间：用一个ListNode，只要记下最前面的X即可， 因为可以调用next不断向后遍历。
细节：1.小心99999多加一个点的问题。
实现1，用stack：
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode plusOne(ListNode head) { Stack<ListNode> stack = new Stack<>(); ListNode dummy = new ListNode(0); dummy.next = head; while (head != null) { if (head.val != 9) { stack.clear(); } stack.push(head); head = head.next; } ListNode crt = null; while (!stack.isEmpty()) { crt = stack.pop(); crt.val = (crt.val + 1) % 10; } if (crt != null && crt.val == 0) { ListNode newN = new ListNode(1); newN.next = dummy.next; dummy.next = newN; } return dummy.next; } }
实现2，用指针：
/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode plusOne(ListNode head) { Stack<ListNode> stack = new Stack<>(); ListNode dummy = new ListNode(0); dummy.next = head; ListNode change = head; // find the start point of those node that need change while (head != null) { if (head.val != 9) { change = head; } head = head.next; } // for the special case of 99999999... if (change.val == 9) { ListNode newN = new ListNode(1); newN.next = change; dummy.next = newN; } // make the add one change while (change != null) { change.val = (change.val + 1) % 10; change = change.next; } return dummy.next; } }
leetcode369- Plus One Linked List- medium
标签：self most 出现 public ini ext git red for
原文地址：http://www.cnblogs.com/jasminemzy/p/7976841.html
