hdu 5343 MZL's Circle Zhou（后缀自动机）

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
typedef unsigned long long ll;
const int maxn = 90005;
const int SIGMA_SIZE = 26;

struct SAM {
int sz, last;
int g[maxn<<1][SIGMA_SIZE], pre[maxn<<1], step[maxn<<1];
int pos[maxn<<1];
ll tot, right[maxn<<1], cnt[maxn<<1], dp[maxn<<1];

void newNode(int s) {
step[++sz] = s;
pre[sz] = 0;
memset(g[sz], 0, sizeof(g[sz]));
}

int idx(char ch) { return ch -'a'; }

void init() {
tot = 0;
sz = 0, last = 1;
newNode(0);
}

void insert(char ch);
void get_tuopu();
void get_right(char* str);

ll solve(ll* c);
void presolve(ll* c);
}SA, SB;

char a[maxn], b[maxn];

int main () {
int cas;
scanf("%d", &cas);
while (cas--) {
scanf("%s%s", a, b);
int na = strlen(a); SA.init();
for (int i = 0; i < na; i++) SA.insert(a[i]);
int nb = strlen(b); SB.init();
for (int i = nb-1; i >= 0; i--) SB.insert(b[i]);

ll c[30];
memset(c, 0, sizeof(c));
SB.presolve(c);
printf("%llu\n", SA.solve(c));
}
return 0;
}

void SAM::presolve(ll* c) {
get_tuopu();
memset(dp, 0, sizeof(dp));
dp[1] = 1;

for (int i = 1; i <= sz; i++) {
int u = pos[i];
for (int j = 0; j < SIGMA_SIZE; j++) {
int v = g[u][j];
if (v == 0) continue;
c[j] += dp[u];
dp[v] += dp[u];
}
}
}

ll SAM::solve(ll* c) {
get_tuopu();

memset(dp, 0, sizeof(dp));
dp[1] = 1;

ll ret = 0;
for (int i = 1; i <= sz; i++) {
int u = pos[i];
for (int j = 0; j < SIGMA_SIZE; j++) {
int v = g[u][j];
if (v == 0) ret += dp[u] * c[j];
else dp[v] += dp[u];
}
ret += dp[u];
}
return ret;
}

void SAM::insert(char ch) {
newNode(step[last] + 1);
int v = idx(ch), p = last, np = sz;

while (p && !g[p][v]) {
g[p][v] = np;
p = pre[p];
}

if (p) {
int q = g[p][v];
if (step[q] == step[p] + 1)
pre[np] = q;
else {
newNode(step[p] + 1);
int nq = sz;
for (int j = 0; j < SIGMA_SIZE; j++) g[nq][j] = g[q][j];

pre[nq] = pre[q];
pre[np] = pre[q] = nq;

while (p && g[p][v] == q) {
g[p][v] = nq;
p = pre[p];
}
}
} else
pre[np] = 1;

tot += step[np] - step[pre[np]];
last = np;
}

void SAM::get_tuopu() {
for (int i = 0; i <= sz; i++) cnt[i] = 0;
for (int i = 1; i <= sz; i++) cnt[step[i]]++;
for (int i = 1; i <= sz; i++) cnt[i] += cnt[i-1];
for (int i = 1; i <= sz; i++) pos[cnt[step[i]]--] = i;
}

void SAM::get_right(char* str) {
int p = 1, n = strlen(str);
for (int i = 0; i <= sz; i++) right[i] = 0;

for (int i = 0; i < n; i++) {
int v = idx(str[i]);
p = g[p][v];
right[p]++;
}

for (int i = sz; i; i--) {
int u = pos[i];
right[pre[u]] += right[u];
}
}