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:
");
    while (temp != NULL)
    {
        printf("%d ", temp->val);
        temp = temp->next;
    }
    printf("
");
}

// 获取链表长度
int getListLength(ListNode* head)
{
    int length = 0;
    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 = 0; i < diff; ++i)
        longList = longList->next;
    
    while (longList && shortList && shortList!=longList)
    {
        longList = longList->next;
        shortList = shortList->next;
    }
    
    if (longList == NULL)
        printf("Not Find
");
    else
        printf("Find %d
", longList->val);
    
    return longList;
}

int main()
{
    // 测试链表结构
    ListNode* head1 = (ListNode*)malloc(sizeof(ListNode));
    head1->val = 1;
    ListNode* p1 = head1;
    for (int i = 0; i < 4; ++i)
    {
        ListNode* q1 = (ListNode*)malloc(sizeof(ListNode));
        q1->val = i + 2;
        p1->next = q1;
        p1 = q1;
    }
    p1->next = NULL;
    
    
    ListNode* head2 = (ListNode*)malloc(sizeof(ListNode));
    head2->val = 6;
    ListNode* p2 = head2;
    for (int i = 0; i < 4; ++i)
    {
        ListNode* q2 = (ListNode*)malloc(sizeof(ListNode));
        q2->val = i + 7;
        p2->next = q2;
        p2 = q2;
    }
    p2->next = NULL;
    
    p1->next = head2->next->next;
    
    PrintList(head1);
    PrintList(head2);
    
    FindFirstCommonNode(head1, head2);
}