SDOI2008 Sandy的卡片( 后缀数组 )

求出后缀数组, 然后二分答案, 对height数组分组检验答案. 时间复杂度O(|S| log|S|)

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#include<cstdio>

#include<cctype>

#include<cstring>

#include<algorithm>

using namespace std;

const int maxn = 1009;

const int maxN = 1000009;

inline int read() {

char c = getchar();

for(; !isdigit(c); c = getchar());

int ret = 0;

for(; isdigit(c); c = getchar())

ret = ret * 10 + c - ‘0‘;

return ret;

}

bool vis[maxn];

int str[maxn][maxn], len[maxn], n, Top;

int S[maxN], Id[maxN], stk[maxN], N;

int cnt[maxN], Sa[maxN], Height[maxN], Rank[maxN];

void Build(int m) {

int *x = Height, *y = Rank;

for(int i = 0; i < m; i++) cnt[i] = 0;

for(int i = 0; i < N; i++) cnt[x[i] = S[i]]++;

for(int i = 1; i < m; i++) cnt[i] += cnt[i - 1];

for(int i = N; i--; ) Sa[--cnt[x[i]]] = i;

for(int k = 1, p = 0; k <= N; k <<= 1, p = 0) {

for(int i = N - k; i < N; i++) y[p++] = i;

for(int i = 0; i < N; i++)

if(Sa[i] >= k) y[p++] = Sa[i] - k;

for(int i = 0; i < m; i++) cnt[i] = 0;

for(int i = 0; i < N; i++) cnt[x[y[i]]]++;

for(int i = 1; i < m; i++) cnt[i] += cnt[i - 1];

for(int i = N; i--; ) Sa[--cnt[x[y[i]]]] = y[i];

swap(x, y);

p = 1;

x[Sa[0]] = 0;

for(int i = 1; i < N; i++) {

if(y[Sa[i]] != y[Sa[i - 1]] || y[Sa[i] + k] != y[Sa[i - 1] + k]) p++;

x[Sa[i]] = p - 1;

}

if(p >= N) break;

m = p;

}

for(int i = 0; i < N; i++) Rank[Sa[i]] = i;

Height[0] = 0;

for(int i = 0, h = 0; i < N; i++) if(Rank[i]) {

if(h) h--;

while(S[i + h] == S[Sa[Rank[i] - 1] + h]) h++;

Height[Rank[i]] = h;

}

}

void Init() {

int mn = 1 << 30, mx = -1 << 30;

n = read();

for(int i = 0; i < n; i++) {

len[i] = read();

for(int j = 0; j < len[i]; j++) str[i][j] = read();

for(int j = len[i]; --j; ) {

str[i][j] -= str[i][j - 1];

mn = min(mn, str[i][j]);

mx = max(mx, str[i][j]);

}

}

N = 0;

for(int i = 0; i < n; i++) {

for(int j = 1; j < len[i]; j++) {

S[N] = str[i][j] - mn + n;

Id[N++] = i;

}

S[N] = n - i - 1;

Id[N++] = n;

}

Build(mx - mn + n + 1);

memset(vis, 0, sizeof vis);

vis[n] = 1;

Top = 0;

}

bool chk(int v) {

while(Top) vis[stk[--Top]] = 0;

for(int i = 1; i < N; i++) if(Height[i] >= v) {

if(!vis[Id[Sa[i - 1]]])

vis[stk[Top++] = Id[Sa[i - 1]]] = 1;

if(!vis[Id[Sa[i]]])

vis[stk[Top++] = Id[Sa[i]]] = 1;

if(Top >= n) return true;

} else {

while(Top) vis[stk[--Top]] = 0;

}

return false;

}

void Work() {

int l = 1, r = maxN, ans = 0;

while(l <= r) {

int m = (l + r) >> 1;

if(chk(m)) {

ans = m, l = m + 1;

}

else

r = m - 1;

}

printf("%d\n", ++ans);

}

int main() {

Init();

Work();

return 0;

}

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