题解 | #链表相加(二)# C头插法反转链表后相加值赋予头插法创建新链表

 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 *
 * C语言声明定义全局变量请加上static，防止重复定义
 */

/**
 * 
 * @param head1 ListNode类 
 * @param head2 ListNode类 
 * @return ListNode类
 */
struct ListNode* addInList(struct ListNode* head1, struct ListNode* head2 ) {
    // write code here
    struct ListNode* H1=malloc(sizeof(struct ListNode));
    struct ListNode* H2=malloc(sizeof(struct ListNode));
    struct ListNode* p,*q;
    H1->next=NULL;
    H2->next=NULL;
    //头插法两个链表反转
    while(head1!=NULL&&head2!=NULL)
    {
        p=head1;
        q=head2;
        head1=head1->next;
        head2=head2->next;
        p->next=H1->next;
        H1->next=p;
        q->next=H2->next;
        H2->next=q;
    }
    //长度不同的特殊处理
    while(head1!=NULL)
    {
        p=head1;
        head1=head1->next;
        p->next=H1->next;
        H1->next=p;
    }
    while(head2!=NULL)
    {
        q=head2;
        head2=head2->next;
        q->next=H2->next;
        H2->next=q;
    }
    head1=H1->next;
    head2=H2->next;
    int sum;
    int add=0;
    H1->next=NULL;
    //值相加，头插法创建新链表
    while(head1!=NULL||head2!=NULL)
    {
        struct ListNode* temp=malloc(sizeof(struct ListNode));
        int a=0,b=0;
        if(head1!=NULL)
            a=head1->val;
        else
            a=0;
        if(head2!=NULL)
            b=head2->val;
        else
            b=0;     
        sum=(a+b+add);
        add=sum/10;
        sum=sum%10;
        temp->val=sum;
        temp->next=H1->next;
        H1->next=temp;
        if(head1!=NULL)
        head1=head1->next;
        if(head2!=NULL)
        head2=head2->next;
    }
    //最终若有进位值特殊处理
    if(add==1)
    {
        p=H1;
        struct ListNode* temp=malloc(sizeof(struct ListNode));
        temp->val=1;
        temp->next=H1->next;
        H1->next=temp;
    }
    return H1->next;
}