You are given the head of a non-empty linked list representing a non-negative integer without leading zeroes.
Return the head of the linked list after doubling it.
Example 1:
Input: head = [1,8,9] Output: [3,7,8] Explanation: The figure above corresponds to the given linked list which represents the number 189. Hence, the returned linked list represents the number 189 * 2 = 378.
Example 2:
Input: head = [9,9,9] Output: [1,9,9,8] Explanation: The figure above corresponds to the given linked list which represents the number 999. Hence, the returned linked list reprersents the number 999 * 2 = 1998.
Constraints:
[1, 104]0 <= Node.val <= 90 itself.
class Solution {
public ListNode reverseLL(ListNode head){
ListNode curr = head ;
ListNode pre = null ;
while(curr!=null){
ListNode temp = curr.next ;
curr.next = pre ;
pre = curr ;
curr = temp ;
}
return pre ;
}
public ListNode doubleIt(ListNode head) {
ListNode nhead = reverseLL(head);
ListNode dummy = new ListNode(-1);
ListNode ans = dummy ;
int carry = 0 ;
while(nhead!=null){
int sum = nhead.val + nhead.val + carry ;
int d = sum%10 ;
carry = sum/10 ;
ListNode temp = new ListNode(d);
dummy.next = temp ;
dummy = dummy.next ;
nhead= nhead.next ;
}
if(carry>0){
ListNode temp = new ListNode(carry);
dummy.next = temp ;
}
ans = reverseLL(ans.next);
return ans ;
}
}
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