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Description
给一个长度为n的字符串,Ti表示i为后缀的字符串,求:
Sample Input
cacao
Sample Output
54
后缀数组+并查集套路题,没什么好说的。。。
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int _min(int x, int y) {return x < y ? x : y;}
typedef unsigned long long ULL;
typedef long long LL;
const ULL P = 131;
struct node {
int x, id;
} height[510000];
LL f[510000];
char ss[510000];
ULL s[510000], o[510000];
int n, m, a[510000], Rank[510000], Rsort[510000], sa[510000], yy[510000];
int fa[510000], tot[510000];
bool cmp(node a, node b) {return a.x > b.x;}
int findfa(int x) {
if(fa[x] != x) fa[x] = findfa(fa[x]);
return fa[x];
}
void get_sa() {
memcpy(Rank, a, sizeof(Rank));
for(int i = 1; i <= n; i++) Rsort[Rank[i]]++;
for(int i = 1; i <= m; i++) Rsort[i] += Rsort[i - 1];
for(int i = n; i >= 1; i--) sa[Rsort[Rank[i]]--] = i;
int ln = 1, p;
while(p < n) {
int k = 0;
for(int i = n - ln + 1; i <= n; i++) yy[++k] = i;
for(int i = 1; i <= n; i++) if(sa[i] - ln > 0) yy[++k] = sa[i] - ln;
memset(Rsort, 0, sizeof(Rsort));
for(int i = 1; i <= n; i++) Rsort[Rank[i]]++;
for(int i = 1; i <= m; i++) Rsort[i] += Rsort[i - 1];
for(int i = n; i >= 1; i--) sa[Rsort[Rank[yy[i]]]--] = yy[i];
for(int i = 1; i <= n; i++) yy[i] = Rank[i];
p = 1; Rank[sa[1]] = 1;
for(int i = 2; i <= n; i++) {
if(yy[sa[i]] != yy[sa[i - 1]] || yy[sa[i] + ln] != yy[sa[i - 1] + ln]) p++;
Rank[sa[i]] = p;
} m = p, ln *= 2;
}
}
LL sum(int x) {return (LL)x * (x - 1) / 2;}
int main() {
scanf("%s", ss + 1);
n = strlen(ss + 1);
for(int i = 1; i <= n; i++) a[i] = ss[i] - 'a' + 1;
o[0] = 1; for(int i = 1; i <= n; i++) o[i] = o[i - 1] * P, s[i] = s[i - 1] * P + a[i];
m = 26; get_sa();
LL ans = (LL)(n + 1) * n / 2 * (n - 1);
for(int i = 1; i < n; i++) {
int x = sa[i], y = sa[i + 1];
int l = 1, r = _min(n - x + 1, n - y + 1), ans = 0;
while(l <= r) {
int mid = (l + r) / 2;
if(s[x + mid - 1] - s[x - 1] * o[mid] == s[y + mid - 1] - s[y - 1] * o[mid]) l = mid + 1, ans = mid;
else r = mid - 1;
} height[i].x = ans, height[i].id =i;
} sort(height + 1, height + n, cmp);
for(int i = 1; i <= n; i++) fa[i] = i, tot[i] = 1;
LL hh = 0, u = height[1].x;
for(int i = 1; i < n; i++) {
if(height[i].x != height[i - 1].x && i != 1) f[height[i - 1].x] = hh;
if(height[i].x == 0) break;
int x = sa[height[i].id], y = sa[height[i].id + 1];
int fx = findfa(x), fy = findfa(y);
hh -= sum(tot[fx]), hh -= sum(tot[fy]);
tot[fy] += tot[fx], fa[fx] = fy;
hh += sum(tot[fy]);
} if(height[n - 1].x) f[height[n - 1].x] = hh;
for(int i = 1; i <= u; i++) {
f[i] -= f[i + 1];
ans -= f[i] * i * 2;
} printf("%lld\n", ans);
return 0;
}