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 ) {
    if(pHead1 == NULL || pHead2 == NULL) return NULL;
    struct ListNode* p1 = pHead1;
    struct ListNode* p2 = pHead2;
    int i = 0, j = 0;
    while(p1 != p2){
        p1 = p1->next;
        p2 = p2->next;
        if(p1 == NULL){
            p1 = pHead2;
            i++;
        }
        if(p2 == NULL){
            p2 = pHead1;
            j++;
        }
        if(i == 2 || j == 2) return NULL;
    }
    return p1;
    // write code here
}