两数相加——链表，leetcode第二题思路

import org.w3c.dom.NodeList;

public class Solution2 {
    public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummyhead = new ListNode(0);
        ListNode p = l1, q = l2, curr = dummyhead;
        int addOne = 0;
        //考虑validation
        while (p == null || q == null || curr == null) {
            return null;
        }
        while (p != null || q != null) {
            int x = (p != null) ? p.val : 0;
            int y = (q != null) ? q.val : 0;
            int sum = addOne + x + y;
            addOne = sum / 10;
            curr.next = new ListNode(sum % 10);
            curr = curr.next;
            if (p != null) {
                p = p.next;
            }
            if (q != null) {
                q = q.next;
            }
            if (addOne > 0) {
                curr.next = new ListNode(addOne);
            }

        }
        return dummyhead.next;
    }


    static class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }
    public static String print(ListNode l){
        StringBuilder builder=new StringBuilder();
        while(l!=null){
            builder.append(l.val);
            l=l.next;
        }

        return builder.toString();

    }

    /**
     * @测试部分
     */
    public static void main(String args[]) {
        ListNode l1=new ListNode(2);
        ListNode l2=new ListNode(5);
        l1.next=new ListNode(4);
        l2.next=new ListNode(6);
        l1.next.next=new ListNode(3);
        l2.next.next=new ListNode(4);
        System.out.println(print(addTwoNumbers(l1,l2)));
    }
}

 

import org.w3c.dom.NodeList;

public class Solution2 {
public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode dummyhead = new ListNode(0);
ListNode p = l1, q = l2, curr = dummyhead;
int addOne = 0;
//考虑validation
while (p == null || q == null || curr == null) {
return null;
}
while (p != null || q != null) {
int x = (p != null) ? p.val : 0;
int y = (q != null) ? q.val : 0;
int sum = addOne + x + y;
addOne = sum / 10;
curr.next = new ListNode(sum % 10);
curr = curr.next;
if (p != null) {
p = p.next;
}
if (q != null) {
q = q.next;
}
if (addOne > 0) {
curr.next = new ListNode(addOne);
}

        }
return dummyhead.next;
}


static class ListNode {
int val;
ListNode next;

ListNode(int x) {
val = x;
}
    }
public static String print(ListNode l){
StringBuilder builder=new StringBuilder();
while(l!=null){
builder.append(l.val);
l=l.next;
}

return builder.toString();

}

/**
     * @测试部分
*/
public static void main(String args[]) {
ListNode l1=new ListNode(2);
ListNode l2=new ListNode(5);
l1.next=new ListNode(4);
l2.next=new ListNode(6);
l1.next.next=new ListNode(3);
l2.next.next=new ListNode(4);
System.out.println(print(addTwoNumbers(l1,l2)));
}
}