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！
1 #include <stdio.h> 2 #include <string.h> 3 #include <iostream> 4 #include <algorithm> 5 #include <queue> 6 #include <map> 7 #include <set> 8 #include <vector> 9 #include <string> 10 #include <math.h> 11 using namespace std; 12 13 int HASH; 14 const int MAXN = 100010; 15 int now ; 16 struct HASHMAP 17 { 18 int head[10007],next[MAXN],size; 19 unsigned long long state[MAXN]; 20 int f[MAXN]; 21 void init() 22 { 23 size = 0; 24 for(int i = 0;i < HASH ;i++) 25 head[i] = -1; 26 //memset(head,-1,sizeof(head)); 27 } 28 int insert(unsigned long long val,int _id) 29 { 30 int h = val % HASH; 31 for(int i = head[h];i != -1;i = next[i]) 32 { 33 if(val == state[i]) 34 { 35 int tmp = f[i]; 36 f[i] = _id; 37 return tmp; 38 } 39 } 40 f[size] = _id; 41 state[size] = val; 42 next[size] = head[h]; 43 head[h] = size++; 44 return 0; 45 } 46 }H; 47 48 const int SEED = 13331; 49 unsigned long long P[MAXN]; 50 unsigned long long S[MAXN]; 51 unsigned long long a[MAXN]; 52 char str[MAXN]; 53 54 int main() 55 { 56 //freopen("in.txt","r",stdin); 57 //freopen("out.txt","w",stdout); 58 P[0] = 1; 59 for(int i = 1;i < MAXN;i++) 60 P[i] = P[i-1]*SEED; 61 int M,L; 62 now = -1; 63 while(scanf("%d%d",&M,&L) == 2) 64 { 65 now --; 66 scanf("%s",str); 67 int n = strlen(str); 68 S[0] = 0; 69 for(int i = 1;i <= n;i++) 70 S[i] = S[i-1]*SEED + str[i-1]; 71 int ans = 0; 72 if(L>= 300) 73 HASH = 10007; 74 else 75 HASH = 107; 76 for(int st = 1;st <= L;st++) 77 { 78 H.init(); 79 int tmp = 1; 80 int cnt = 0; 81 for(int i = st; i + L - 1 <= n;i += L) 82 a[++cnt] = S[i+L - 1] - S[i-1] * P[L]; 83 /* 84 for(int i = 1;i <= cnt;i++) 85 cout<<a[i]<<" "; 86 cout<<endl; 87 */ 88 for(int i = 1;i <= cnt;i++) 89 { 90 int l = H.insert(a[i],i); 91 if(i - l >= M)continue; 92 ans += max(0, i - M - tmp + 1); 93 tmp = max(tmp,l + 1); 94 //printf("%d %d ",tmp,l); 95 } 96 ans += max(0,cnt+1 - M - tmp+1); 97 } 98 printf("%d ",ans); 99 } 100 return 0; 101 } 102 /* 103 1 104 17239715954 17239715954 17417444844 17239715954 105 1 0 106 2 1 107 3 2 108 2 109 17417444844 17417444845 17595133743 110 1 0 111 1 0 112 3 113 17595133744 17595147076 17239702622 114 1 0 115 1 0 116 0 117 */