剑指Offer35 两个链表第一个公共结点

 /*************************************************************************
     > File Name: 35_FirstCommonNode.cpp
     > Author: Juntaran
     > Mail: JuntaranMail@gmail.com
     > Created Time: 2016年09月02日 星期五 20时52分28秒
  ************************************************************************/

 #include <stdio.h>
 #include <malloc.h>

 // 链表结构体
 struct ListNode
 {
     int val;
     struct ListNode* next;
 };

 // 顺序输出链表
 void PrintList(ListNode* head)
 {
     if (head == NULL)
         return;
     ListNode* temp = head;
     printf("PrintList:\n");
     while (temp != NULL)
     {
         printf("%d ", temp->val);
         temp = temp->next;
     }
     printf("\n");
 }

 // 获取链表长度
 int getListLength(ListNode* head)
 {
     int length = ;
     ListNode* p = head;
     while (p)
     {
         length ++;
         p = p->next;
     }
     return length;
 }

 // 寻找第一个公共结点
 ListNode* FindFirstCommonNode(ListNode* head1, ListNode* head2)
 {
     int length1 = getListLength(head1);
     int length2 = getListLength(head2);

     ListNode* longList;
     ListNode* shortList;
     int diff;

     if (length1 >= length2)
     {
         longList = head1;
         shortList = head2;
         diff = length1 - length2;
     }
     else
     {
         longList = head2;
         shortList = head1;
         diff = length2 - length1;
     }

     for (int i = ; i < diff; ++i)
         longList = longList->next;

     while (longList && shortList && shortList!=longList)
     {
         longList = longList->next;
         shortList = shortList->next;
     }

     if (longList == NULL)
         printf("Not Find\n");
     else
         printf("Find %d\n", longList->val);

     return longList;
 }

 int main()
 {
     // 测试链表结构
     ListNode* head1 = (ListNode*)malloc(sizeof(ListNode));
     head1->val = ;
     ListNode* p1 = head1;
     for (int i = ; i < ; ++i)
     {
         ListNode* q1 = (ListNode*)malloc(sizeof(ListNode));
         q1->val = i + ;
         p1->next = q1;
         p1 = q1;
     }
     p1->next = NULL;

     ListNode* head2 = (ListNode*)malloc(sizeof(ListNode));
     head2->val = ;
     ListNode* p2 = head2;
     for (int i = ; i < ; ++i)
     {
         ListNode* q2 = (ListNode*)malloc(sizeof(ListNode));
         q2->val = i + ;
         p2->next = q2;
         p2 = q2;
     }
     p2->next = NULL;

     p1->next = head2->next->next;

     PrintList(head1);
     PrintList(head2);

     FindFirstCommonNode(head1, head2);
 }