public ListNode AddTwoNumbers(ListNode l1, ListNode l2, int carry)
{
int value1 = 0;
int value2 = 0;
if (l1 != null) //Key1: Length of l1 and l2 may not equal.
{
value1 = l1.val;
}
if (l2 != null)
{
value2 = l2.val;
}
if (l1 != null || l2 != null)
{
int currentValue = (value1 + value2 + carry) % 10; //Key2: Add carry
int currentCarry = (value1 + value2 + carry) / 10;
ListNode node = new ListNode(currentValue);
node.next = AddTwoNumbers(l1 == null ? null : l1.next, l2 == null ? null : l2.next, currentCarry);
return node;
}
if (carry != 0) //Key3: Even l1 and l2 are end, the carry may not.
{
return new ListNode(carry);
}
return null;
}
public ListNode AddTwoNumbers(ListNode l1, ListNode l2)
{
if (l1 == null || l2 == null)
return null;
int currentValue = (l1.val + l2.val) % 10;
int currentCarry = (l1.val + l2.val) / 10;
ListNode node = new ListNode(currentValue);
node.next = AddTwoNumbers(l1.next, l2.next, currentCarry);
return node;
}
public void DoIt()
{
//(2 -> 4 -> 3) + (5 -> 6 -> 4) ==> 7 -> 0 -> 8
//ListNode l1 = new ListNode(2);
//l1.next = new ListNode(4);
//l1.next.next = new ListNode(3);
//ListNode l2 = new ListNode(5);
//l2.next = new ListNode(6);
//l2.next.next = new ListNode(4);
//1->8 + 0 => 1->8
//ListNode l1 = new ListNode(1);
//l1.next = new ListNode(8);
//ListNode l2 = new ListNode(0);
//1 + 9-> 9 => 1->0->0
ListNode l1 = new ListNode(1);
ListNode l2 = new ListNode(9);
l2.next = new ListNode(9);
ListNode add = AddTwoNumbers(l1, l2);
while (add != null)
{
Console.WriteLine(add.val);
add = add.next;
}
}
