D. Match & Catch

能够用各种方法做。字符串hash。后缀数组，dp。拓展kmp，字典树。。

。

字符串hash（模板）

http://blog.csdn.net/gdujian0119/article/details/6777239

BKDR Hash Function  ：

// BKDR Hash Function
unsigned int BKDRHash(char *str)
{  unsigned int seed = 131; // 31 131 1313 13131 131313 etc..  unsigned int hash = 0;  while (*str)  {  hash = hash * seed + (*str++);  }  return (hash & 0x7FFFFFFF);
}  

本题hash解法 n^2

#define ULL unsigned long long
const int maxn = 5111 * 2;const int HASH = 10007;
struct HashMap{int head[HASH];int next[maxn];ULL state[maxn];int num_s1[maxn];int num_s2[maxn];int sz;void init(){sz = 0;memset(head, -1, sizeof(head));}int insert(ULL val, bool info){int h = val % HASH;for (int i = head[h]; i != -1; i = next[i]){if (val == state[i]){if (info) num_s1[i]++;else num_s2[i]++;return 1;///存在}}num_s1[sz] = 0;num_s2[sz] = 0;state[sz] = val;next[sz] = head[h];if (info) num_s1[sz]++;else num_s2[sz]++;head[h] = sz++;return 0;///不存在}bool check(){for (int i = 0; i < sz; i++){if (num_s1[i] == num_s2[i] && num_s1[i] == 1)return true;}return false;}
}H;const int SEED = 13331;
ULL P[maxn];
ULL s1[maxn], s2[maxn];char sa[maxn], sb[maxn];void hash_pre(ULL P[])
{P[0] = 1;for (int i = 1; i <= maxn; i++)P[i] = P[i - 1] * SEED;
}
void hash_init(ULL s1[], char sa[])///sa[],下标从0開始;相应是s1[]的值得下标从1開始
{int n = strlen(sa);s1[0] = 0;for (int i = 1; i <= n; i++)s1[i] = s1[i - 1] * SEED + sa[i - 1];
}
ULL getSeg(ULL s1[], int l, int r)///求s1[]的下标区间的hash值
{return s1[r] - s1[l - 1] * P[r - l + 1];
}int main()
{hash_pre(P);RS(sa); RS(sb);int n = strlen(sa), m = strlen(sb);hash_init(s1, sa);hash_init(s2, sb);int fla = 0;int mn = min(n, m);for (int i = 1; i <= mn; i++){H.init();for (int j = i; j <= n; j++){H.insert(getSeg(s1, j - i + 1, j), 0);}for (int j = i; j <= m; j++){H.insert(getSeg(s2, j - i + 1, j), 1);}if (H.check()){printf("%d\n", i);fla = 1;break;}}if (!fla) puts("-1");return 0;
}

后缀数组：

const int MAXN = 5111 * 2;
const int INF = 0x3f3f3f3f;
int wa[MAXN], wb[MAXN], wv[MAXN], wn[MAXN];
//char r[MAXN];
int a[MAXN], sa[MAXN], rank[MAXN], height[MAXN];int cmp(int *r, int a,int b, int k)
{return r[a] == r[b] && r[a + k] == r[b + k];
}
void build_sa(int *r, int *sa, int n,int m)
{int i,j, p;int *x = wa, *y = wb, *t;for (int i= 0; i < m; i++) wn[i] = 0;for (int i= 0; i < n; i++) wn[x[i] = r[i]]++;for (int i = 1; i < m; i++) wn[i] += wn[i - 1];for (int i = n - 1; i >= 0; i--) sa[--wn[x[i]]] = i;for (p = 1, j = 1; p < n; j <<= 1, m = p){for (p = 0, i = n - j; i < n; i++) y[p++] = i;for (i = 0; i < n; i++) if (sa[i] >= j) y[p++] = sa[i] - j;for (i = 0; i < m; i++) wn[i] = 0;for (i = 0; i < n; i++) wn[wv[i] = x[y[i]]]++;for (i = 1; i < m; i++) wn[i] += wn[i - 1];for (i = n - 1; i >= 0; i--) sa[--wn[wv[i]]] = y[i];t = x; x = y; y = t;x[sa[0]] = 0; p = 1;for (i = 1; i < n; i++)x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;}
}
void getHeight(int *r, int *sa, int n)
{int i, j, k = 0;for (i = 1; i <= n; i++){rank[sa[i]] = i;height[i] = 0;}for (i = 0;i < n; i++){if (k) k--;j = sa[rank[i] - 1];while (r[i + k] == r[j + k]) k++;height[rank[i]] = k;}
}char ca[MAXN], cb[MAXN];void solve(int n)
{height[n + 1] = 0;int ans = INF;int l = strlen(ca);for (int i = 1; i <= n; i++){if (!height[i]) continue;if (sa[i] < l && sa[i - 1] < l) continue;if (sa[i] >= l && sa[i - 1] >= l) continue;int pre = height[i - 1] + 1;int next = height[i + 1] + 1;if (height[i] >= max(pre, next)){ans = min(ans, max(pre, next));}}if (ans == INF) puts("-1");else printf("%d\n", ans);
}
int main()
{int t, n, m;///n, mn = 0;m = 256;RS(ca);int l = strlen(ca);REP(j, l) a[n++] = (int)ca[j];a[n++] = m++;RS(cb);l = strlen(cb);REP(j, l) a[n++] = (int)cb[j];a[n++] = m++;a[--n] = 0; --m;build_sa(a, sa, n + 1, m);getHeight(a, sa, n);solve(n);return 0;
}
/*
0 8 0
1 6 0
2 4 2
3 2 4
4 0 6
5 7 0
6 5 1
7 3 3
8 1 5
^^^^^^^^^^^^^^0 4
1 8
2 3
3 7
4 2
5 6
6 1
7 5
8 0
^^^^^^^^^^^^^^
*/