cf244D. Match & Catch 字符串hash （模板）或 后缀数组。。。

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);
}

#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;
}

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, m
n = 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
^^^^^^^^^^^^^^
*/