2. Add Two Numbers

Question

2. Add Two Numbers

Solution

题目大意：两个链表对应的元素相加，满10进1，反两个链表相加后的链表

思路：同时遍历两个链表，同时构造相加后的链表，满10进1，用一个数来记录进位

Java实现：

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    ListNode ans = new ListNode(0);
    ListNode curL1 = l1;
    ListNode curL2 = l2;
    ListNode curAns = ans;
    int last = 0;
    ListNode curAnsPre = ans;
    while (curL1 != null || curL2 != null) {
        int valL1 = 0;
        int valL2 = 0;
        if (curL1 != null) {
            valL1 = curL1.val;
            curL1 = curL1.next;
        }
        if (curL2 != null) {
            valL2 = curL2.val;
            curL2 = curL2.next;
        }
        curAns.val = valL1 + valL2 + last;
        if (curAns.val >= 10) {
            curAns.val -= 10;
            last = 1;
        } else {
            last = 0;
        }
        curAns.next = new ListNode(1);
        curAnsPre = curAns;
        curAns = curAns.next;
    }
    curAnsPre.next = last == 0 ? null : curAnsPre.next;
    return ans;
}