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FindFirstCommonNode.c
119 lines (88 loc) · 2.09 KB
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FindFirstCommonNode.c
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/*
* 两个链表的第一个公共结点
*/
#include<stdio.h>
#include<stdlib.h>
struct
ListNode{
int m_nKey;
ListNode* m_pNext;
};
typedef struct ListNode node_t;
node_t*
create_node(int e)
{
node_t *pnode = ( node_t* )malloc( sizeof( node_t ) );
pnode->m_nKey = e;
pnode->m_pNext = NULL;
return pnode;
}
void
connect(node_t* pnode1, node_t* pnode2)
{
if( pnode1 == NULL )
return ;
pnode1->m_pNext = pnode2;
}
int
GetListLength( node_t* head )
{
unsigned int length = 0;
node_t* node = head;
while(node != NULL){
++length;
node = node->m_pNext;
}
return length;
}
node_t*
FindFirstCommonNode(node_t* pHead1, node_t* pHead2)
{
/*得到两个链表的长度*/
unsigned int length1 = GetListLength( pHead1 );
unsigned int length2 = GetListLength( pHead2 );
int lenght_diff = length1 - length2;
node_t* pListHeadLong = pHead1;
node_t* pListHeadShort = pHead2;
if( length1 < length2){
pListHeadLong = pHead2;
pListHeadShort = pHead1;
lenght_diff = length2 - length1;
}
/*先在长的链表上走几步，在同时在两个表上遍历查询*/
for(int i = 0; i < lenght_diff; i++){
pListHeadLong = pListHeadLong->m_pNext;
}
while( pListHeadLong != NULL
&& pListHeadShort != NULL
&& pListHeadLong != pListHeadShort )
{
pListHeadLong = pListHeadLong->m_pNext;
pListHeadShort =pListHeadShort->m_pNext;
}
node_t* firstcommonnode = pListHeadLong;
return firstcommonnode;
}
void
main()
{
node_t* pnode1 = create_node(1);
node_t* pnode2 = create_node(2);
node_t* pnode3 = create_node(3);
node_t* pnode4 = create_node(4);
node_t* pnode5 = create_node(5);
node_t* pnode6 = create_node(6);
node_t* pnode7 = create_node(7);
/*List1*/
connect(pnode1, pnode2);
connect(pnode2, pnode3);
connect(pnode3, pnode6);
connect(pnode6, pnode7);
/*List2*/
connect(pnode4, pnode5);
connect(pnode5, pnode6);
node_t* pHead1 = pnode1;
node_t* pHead2 = pnode4;
node_t* common_node = FindFirstCommonNode(pHead1, pHead2);
printf("The first common node is %d\n", common_node->m_nKey);
}