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
 */
 #include <math.h>
#include <stdio.h>
struct ListNode* FindFirstCommonNode(struct ListNode* pHead1, struct ListNode* pHead2 ) 
{
    if(pHead1==NULL&&pHead2!=NULL)return NULL;
    if(pHead1!=NULL&&pHead2==NULL)return NULL;
    if(pHead1==NULL&&pHead2==NULL)return NULL;
    struct ListNode* p=pHead1;
    int count1=1,count2=1;
    while(p->next!=NULL)
    {
        count1++;
        p=p->next;
    }
    p=pHead2;
    while(p->next!=NULL)
    {
        count2++;
        p=p->next;
    }
    struct ListNode* slow=count1>count2?pHead2:pHead1;//slow=p2
    struct ListNode* fast=count1>count2?pHead1:pHead2;//fast=p1
    for(int i=0;i<(abs(count1-count2));i++)
    {
        fast=fast->next;
    }
    while(fast!=slow)
    {
        fast=fast->next;
        slow=slow->next;
    }
    return slow;
}