题解 | #两个链表的第一个公共结点#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

/**
 * 
 * @param pHead1 ListNode类 
 * @param pHead2 ListNode类 
 * @return ListNode类
 */
struct ListNode* FindFirstCommonNode(struct ListNode* pHead1, struct ListNode* pHead2 ) {
    // write code here
    struct ListNode* L1,*L2;
    L1=pHead1;
    L2=pHead2;
    int a=1,b=1;
    if(L1==NULL||L2==NULL)return NULL;
    while(L1->next){
        a++;
        L1=L1->next;
    }
    while(L2->next){
        b++;
        L2=L2->next;
    }
    L1=pHead1;
    L2=pHead2;
    if(a>b){
        a=a-b;
        while(a--){
            L1=L1->next;
        }
    }else{
        a=b-a;
        while(a--){
            L2=L2->next;
        }
    }
    while(L1!=L2){
        L1=L1->next;
        L2=L2->next;
    }

    return L1;
}