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