Created
April 23, 2014 13:50
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bzoj2342
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#include <cstdio> | |
#include <algorithm> | |
const int N = 500000 * 2 + 9; | |
char s[N],r[N]; | |
int n,len[N],fa[N],ans; | |
void init() | |
{ | |
len[0] = 0; | |
for (int i = 1,mp = 0; i < n; ++i) { | |
if (mp + len[mp] >= i) | |
len[i] = std::min(mp + len[mp] - i,len[2 * mp - i]); | |
for (; i - len[i] - 1 >= 0 && i + len[i] + 1 < n && s[i + len[i] + 1] == s[i - len[i] - 1]; ) ++len[i]; | |
if (i + len[i] > mp + len[mp]) mp = i; | |
} | |
} | |
int getf(int x){return x == fa[x] ? x : fa[x] = getf(fa[x]);} | |
int main() | |
{ | |
#ifndef ONLINE_JUDGE | |
freopen("2342.in","r",stdin); | |
freopen("2342.out","w",stdout); | |
#endif | |
scanf("%d\n",&n); | |
scanf("%s",r); | |
int m = 0; | |
s[m++] = '#'; | |
for (int i = 0; i < n; ++i) { | |
s[m++] = r[i]; | |
s[m++] = '#'; | |
} | |
//puts(s); | |
n = m; | |
init(); | |
for (int i = 0; i < n; ++i) fa[i] = (i + 1) / 2 * 2; | |
for (int i = 4,j; i < n; i += 2) { | |
for (j = getf(i - len[i] / 2); j + len[j] < i; j = fa[j]) fa[j] = getf(j + 1); | |
if (j < i) ans = std::max(ans,i - j); | |
} | |
printf("%d\n",ans * 2); | |
} |
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