poj 2887 块状链表 单点插入+单点查询

块状链表第一题，懒得写成链表形式的，所以写成了静态链表。

思想还是很简单的，就是进行分块查找和插入，和建立索引有点像，复杂度是根号的，实现起来比较容易，由于这个题插入操作不多，所以没有写split函数，

因为没有删除操作，所以也没有写union函数，随后有空再补上吧。

  1 #include <iostream>

  2 #include <cstring>

  3 #include <cstdio>

  4 #include <cmath>

  5 using namespace std;

  6 

  7 const int N = 1002001;

  8 const int M = 2000;

  9 char str[N];

 10 

 11 struct Block

 12 {

 13     char ch[M];

 14     int size;

 15     int next;

 16 

 17     void init()

 18     {

 19         size = 0;

 20         next = -1;

 21     }

 22 

 23 };

 24 

 25 struct BlockList

 26 {

 27     int head, len;    

 28     Block b[M];

 29 

 30     void init( char * s )

 31     {

 32         len = strlen(s);

 33         int as = sqrt( ( double ) len );

 34         head = 0;

 35         int j = head;

 36         b[j].init();

 37         for ( int i = 0; i < len; i++ )

 38         {

 39             if ( b[j].size == as )

 40             {

 41                 b[j].next = j + 1;

 42                 j++;                    

 43                 b[j].init();

 44             }

 45             b[j].ch[b[j].size++] = s[i];

 46         }

 47     }

 48 

 49     //插在第pos个元素前面

 50     void insert( int pos, char v )

 51     {

 52         if ( pos > len )

 53         {

 54             int i = head, j = b[head].next;

 55             while ( j != -1 )

 56             {

 57                 i = b[i].next;

 58                 j = b[j].next;

 59             }

 60             b[i].ch[b[i].size++] = v;

 61             len++;

 62             return ;

 63         }

 64         int i = head;        

 65         while ( pos > b[i].size )

 66         {

 67             pos -= b[i].size;

 68             i = b[i].next;

 69         }

 70         for ( int j = b[i].size; j >= pos; j-- )

 71         {

 72             b[i].ch[j] = b[i].ch[j - 1];

 73         }

 74         b[i].ch[pos - 1] = v;

 75         b[i].size++;

 76         len++;

 77         return ;

 78     }

 79 

 80     char at( int pos )

 81     {

 82         int i = head;

 83         while ( pos > b[i].size )

 84         {

 85             pos -= b[i].size;

 86             i = b[i].next;

 87         }

 88         return b[i].ch[pos - 1];

 89     }

 90 

 91 } bl;

 92 

 93 int main()

 94 {

 95     while ( scanf("%s", str) != EOF )

 96     {

 97         bl.init(str);

 98         int n;

 99         char op[2];        

100         scanf("%d", &n);

101         while ( n-- )

102         {

103             scanf("%s", op);

104             if ( op[0] == 'I' )

105             {

106                 char ch[2];                

107                 int p;

108                 scanf("%s%d", ch, &p);

109                 bl.insert( p, ch[0] );

110             }

111             else

112             {

113                 int p;

114                 scanf("%d", &p);

115                 char ans = bl.at(p);

116                 printf("%c\n", ans);

117             }

118         }

119     }

120     return 0;

121 }