后缀数组模板/LCP模板

//后缀数组模板，MANX为数组的大小
//支持的操作有计算后缀数组(sa数组)， 计算相邻两元素的最长公共前缀(height数组)，使用get_height();
//计算两个后缀a, 和b的最长公共前缀，请先使用lcp_init(),再调用get_lcp(a, b)得到
//下面的n是输入字符串的长度+1(n = strlen(s) + 1)， m是模板的范围 m=128表示在字母，数字范围内，可以扩大也可缩小
//s[len] 是插入的一个比输入字符都要小的字符
struct SufArray {
char s[MAXN];
int sa[MAXN], t[MAXN], t2[MAXN], c[MAXN], n, m;
int rnk[MAXN], height[MAXN];//rnk和height数组
int mi[MAXN][20], idxK[MAXN];//用于计算LCP

void init() {
mem0(s);
mem0(height);
}
//读入字符串作为输入
void read_str() {
gets(s);
m = 128;
n = strlen(s);
s[n++] = ' ';
}
void build_sa() {
int *x = t, *y = t2;
rep (i, 0, m - 1) c[i] = 0;
rep (i, 0, n - 1) c[x[i] = s[i]] ++;
rep (i, 1, m - 1) c[i] += c[i - 1];
dec (i, n - 1, 0) sa[--c[x[i]]] = i;
for(int k = 1; k <= n; k <<= 1) {
int p = 0;
rep (i, n - k, n - 1) y[p++] = i;
rep (i, 0, n - 1) if(sa[i] >= k) y[p++] = sa[i] - k;
rep (i, 0, m - 1) c[i] = 0;
rep (i, 0, n - 1) c[x[y[i]]] ++;
rep (i, 0, m - 1) c[i] += c[i - 1];
dec (i, n - 1, 0) sa[--c[x[y[i]]]] = y[i];
swap(x, y);
p = 1;
x[sa[0]] = 0;
rep (i, 1, n - 1) {
x[sa[i]] = y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + k] == y[sa[i] + k] ? p - 1 : p++;
}
if(p >= n) break;
m = p;
}
}
void get_height() {
int k = 0;
rep (i, 0, n - 1) rnk[sa[i]] = i;
rep (i, 0, n - 1) {
if(k) k --;
int j = sa[rnk[i] - 1];
while(s[i + k] == s[j + k]) k ++;
height[rnk[i]] = k;
}
}
void rmq_init(int *a, int n) {
rep (i, 0, n - 1) mi[i][0] = a[i];
for(int j = 1; (1 << j) <= n; j ++) {
for(int i = 0; i + (1<<j) - 1 < n; i ++) {
mi[i][j] = min(mi[i][j - 1], mi[i + (1 << (j - 1))][j - 1]);
}
}
rep (len, 1, n) {
idxK[len] = 0;
while((1 << (idxK[len] + 1)) <= len) idxK[len] ++;
}
}
int rmq_min(int l, int r) {
int len = r - l + 1, k = idxK[len];
return min(mi[l][k], mi[r - (1 << k) + 1][k]);
}
void lcp_init() {
get_height();
rmq_init(height, n);
}
int get_lcp(int a, int b) {
if(a == b) return n - a - 1;
return rmq_min(min(rnk[a], rnk[b]) + 1, max(rnk[a], rnk[b]));
}
void solve() {
}
};