HDU 4821 String（2013长春现场赛I题）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4821

字符串题。

现场使用字符串HASH乱搞的。

枚举开头！

 #include <stdio.h>
 #include <string.h>
 #include <iostream>
 #include <algorithm>
 #include <queue>
 #include <map>
 #include <set>
 #include <vector>
 #include <string>
 #include <math.h>
 using namespace std;

 int HASH;
 const int MAXN = ;
 int now ;
 struct HASHMAP
 {
     int head[],next[MAXN],size;
     unsigned long long state[MAXN];
     int f[MAXN];
     void init()
     {
         size = ;
         for(int i = ;i < HASH ;i++)
             head[i] = -;
         //memset(head,-1,sizeof(head));
     }
     int insert(unsigned long long val,int _id)
     {
         int h = val % HASH;
         for(int i = head[h];i != -;i = next[i])
         {
             if(val == state[i])
             {
                 int tmp = f[i];
                 f[i] = _id;
                 return tmp;
             }
         }
         f[size] = _id;
         state[size] = val;
         next[size] = head[h];
         head[h] = size++;
         return ;
     }
 }H;

 const int SEED = ;
 unsigned long long P[MAXN];
 unsigned long long S[MAXN];
 unsigned long long a[MAXN];
 char str[MAXN];

 int main()
 {
     //freopen("in.txt","r",stdin);
     //freopen("out.txt","w",stdout);
     P[] = ;
     for(int i = ;i < MAXN;i++)
         P[i] = P[i-]*SEED;
     int M,L;
     now = -;
     while(scanf("%d%d",&M,&L) == )
     {
         now --;
         scanf("%s",str);
         int n = strlen(str);
         S[] = ;
         for(int i = ;i <= n;i++)
             S[i] = S[i-]*SEED + str[i-];
         int ans = ;
         if(L>= )
             HASH = ;
         else
             HASH = ;
         for(int st = ;st <= L;st++)
         {
             H.init();
             int tmp = ;
             int cnt = ;
             for(int i = st; i + L -  <= n;i += L)
                 a[++cnt] = S[i+L - ] - S[i-] * P[L];
             /*
             for(int i = 1;i <= cnt;i++)
                 cout<<a[i]<<" ";
             cout<<endl;
             */
             for(int i = ;i <= cnt;i++)
             {
                 int l = H.insert(a[i],i);
                 if(i - l >= M)continue;
                 ans += max(, i - M - tmp + );
                 tmp = max(tmp,l + );
                 //printf("%d %d\n",tmp,l);
             }
             ans += max(,cnt+ - M - tmp+);
         }
         printf("%d\n",ans);
     }
     return ;
 }
 /*
 1
 17239715954 17239715954 17417444844 17239715954
 1 0
 2 1
 3 2
 2
 17417444844 17417444845 17595133743
 1 0
 1 0
 3
 17595133744 17595147076 17239702622
 1 0
 1 0
 0
 */