题解 | #链表相加(二)#

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head1 ListNode类 
     * @param head2 ListNode类 
     * @return ListNode类
     */
    public ListNode addInList (ListNode head1, ListNode head2) {
        ListNode head11 =head1;
        ListNode head22 =head2;
        int len1 = 0;
        int len2 = 0;
        
        //1.首先遍历一次获取链表长度 
        //作用：1).创建数组时确定数组最大长度2).数组相加时确定加到哪个索引处终止3).确认以哪条长链表作为输出链表
        while(head11!=null){
            len1++;
            head11 = head11.next;
        }
        while(head22!=null){
            len2++;
            head22 = head22.next;
        }
        //2.确认 长短链表长度及对应链表
        int maxlen = len1 > len2 ? len1 : len2;
        int minlen = len1 == maxlen ? len2 : len1;
        ListNode maxNode = maxlen == len1? head1:head2;
        ListNode minNode = maxNode == head2? head1:head2;
        //3.标记链表头 指针
        ListNode res = maxNode;
        ListNode resMin = minNode;
        //4.创建2 个数组
        int[] arr1 = new int[maxlen+1];
        int[] arr2 = new int[maxlen+1];
        
        //5链表值存到数组中
        int index = 1;
        while(maxNode!=null){
            arr1[index++] = maxNode.val;
            maxNode = maxNode.next;
        }
        index = 1 +  maxlen - minlen;
        while(minNode!=null){
            arr2[index++] = minNode.val;
            minNode = minNode.next;
        }
        //6数组值相加 进位
        for(int i=maxlen;i>(maxlen-minlen);i--){
            int temp = arr1[i] + arr2[i];
            
            arr1[i] = temp%10;
            int jin = temp/10;
            index = i;
            while(jin!=0){
                index--;
                int ttt = arr1[index]+1;
                arr1[index] = ttt%10 ;
                jin = ttt/10;
            }
        }
        //7选择长链表，及判断数组索引0位值，为0说明输出链表长度与2链表中长链表长度一致
        ListNode tt =res;
        if(arr1[0] == 0){
            index = 1;
            while(tt!=null){
                tt.val = arr1[index++];
                tt = tt.next;
            }
        }else{
            //否则，长链表末尾追加一个节点
            index = 0;
            while(tt!=null){
                tt.val = arr1[index++];
                if(tt.next==null){
                    resMin.val = arr1[maxlen-1];
                    resMin.next = null;
                    tt.next = resMin;
                    break;
                }
                tt = tt.next;
            }
        }
        return res;
    }
}