HDU 5008 Boring String Problem
题目链接
思路：构造后缀数组，利用height的数组能预处理出每个字典序开始的前缀和有多少个（其实就是为了去除重复串），然后每次二分查找相应位置，然后在往前往后找一下sa[i]最小的
代码：
#include
#include
#include
using namespace std; typedef long long ll; const int MAXLEN = 100005; struct Suffix { char str[MAXLEN]; int s[MAXLEN]; int sa[MAXLEN], t[MAXLEN], t2[MAXLEN], c[MAXLEN], n; int rank[MAXLEN], height[MAXLEN]; ll sum[MAXLEN]; void build_sa(int m) { n++; int i, *x = t, *y = t2; for (i = 0; i < m; i++) c[i] = 0; for (i = 0; i < n; i++) c[x[i] = s[i]]++; for (i = 1; i < m; i++) c[i] += c[i - 1]; for (i = n - 1; i >= 0; i--) sa[--c[x[i]]] = i; for (int k = 1; k <= n; k <<= 1) { int p = 0; for (i = n - k; i < n; i++) y[p++] = i; for (i = 0; i < n; i++) if (sa[i] >= k) y[p++] = sa[i] - k; for (i = 0; i < m; i++) c[i] = 0; for (i = 0; i < n; i++) c[x[y[i]]]++; for (i = 0; i < m; i++) c[i] += c[i - 1]; for (i = n - 1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i]; swap(x, y); p = 1; x[sa[0]] = 0; for (i = 1; i < n; i++) 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; } n--; } void getHeight() { int i, j, k = 0; for (i = 1; i <= n; i++) rank[sa[i]] = i; for (i = 0; i < n; i++) { if (k) k--; int j = sa[rank[i] - 1]; while (s[i + k] == s[j + k]) k++; height[rank[i]] = k; } } void getsum() { for (int i = 1; i <= n; i++) sum[i] = sum[i - 1] + n - sa[i] - height[i]; } void init() { n = strlen(str); for (int i = 0; i < n; i++) s[i] = str[i] - 'a' + 1; s[n] = 0; build_sa(27); getHeight(); getsum(); } void query(ll &ls, ll &rs, ll k) { int u = lower_bound(sum + 1, sum + n + 1, k) - sum; if (u == n + 1) { ls = 0; rs = 0; printf("%I64d %I64d\n", ls, rs); return; } int len = k - sum[u - 1] + height[u]; int st = sa[u]; for (int i = u; i > 1; i--) { if (height[i] < len) break; st = min(st, sa[i - 1]); } for (int i = u + 1; i <= n; i++) { if (height[i] < len) break; st = min(st, sa[i]); } ls = st + 1; rs = st + len; printf("%I64d %I64d\n", ls, rs); } void solve() { init(); ll l = 0, r = 0, v; int q; scanf("%d", &q); while (q--) { scanf("%I64d", &v); ll k = (l^r^v) + 1; query(l, r, k); } } } gao; int main() { while (~scanf("%s", gao.str)) { gao.solve(); } return 0; }