链表 2.3

实现一个算法，删除单向链表中间的某个结点，假定你只能访问该结点。

示例

输入：单向链表a->b->c->d->e中的结点c。

结果：不返回任何数据，但该链表变为：a->b->d->e。

分析：因为无法访问待删除结点的前继结点，所以只能通过复制将后续链表整体向前移动一个位置，并删除最后一个多余的结点。显然，当待删除结点为链表的尾结点时（即没有后继），该问题无解。

 1 #include <iostream>
 2 #include <fstream>
 3 #include <assert.h>
 4
 5 using namespace std;
 6
 7 struct Node {
 8     Node(): val(0), next(0) {}
 9     Node( int value ): val(value), next(0) {}
10     int val;
11     Node *next;
12 };
13
14 void removeNode( Node *node );
15
16 int main( int argc, char *argv[] ) {
17     string data_file = "./data.txt";
18     ifstream ifile( data_file.c_str(), ios::in );
19     if( !ifile.is_open() ) {
20         fprintf( stderr, "cannot open file: %s\n", data_file.c_str() );
21         return -1;
22     }
23     int n = 0, k = -1;
24     while( ifile >>n >>k ) {
25         assert( n > 0 && k > 0 && k < n );
26         Node guard, *node = &guard, *target = 0;
27         for( int i = 0; i < n; ++i ) {
28             node->next = new Node();
29             node = node->next;
30             ifile >>node->val;
31             cout <<node->val <<" ";
32             if( i == k-1 ) { target = node; }
33         }
34         cout <<endl;
35         if( target )
36             cout <<"target to remove: " <<target->val <<endl;
37         else
38             cout <<"target to remove: null" <<endl;
39         removeNode( target );
40         node = guard.next;
41         cout <<"result:" <<endl;
42         while( node ) {
43             Node *next = node->next;
44             cout <<node->val <<" ";
45             delete node;
46             node = next;
47         }
48         cout <<endl <<endl;
49     }
50     ifile.close();
51     return 0;
52 }
53
54 void removeNode( Node *node ) {
55     assert( node && node->next );
56     node->val = node->next->val;
57     while( node->next->next ) {
58         node = node->next;
59         node->val = node->next->val;
60     }
61     delete node->next;
62     node->next = 0;
63     return;
64 }

测试文件

2 1
1 3

3 1
1 2 3

3 2
1 2 3

7 1
14 54 96 23 45 12 45

7 2
14 54 96 23 45 12 45

7 6
14 54 96 23 45 12 45