Substrings
Description
You are given a number of case-sensitive strings of alphabetic characters, find the largest string X, such that either X, or its inverse can be found as a substring of any of the given strings.
Input
The first line of the input contains a single integer t (1 <= t <= 10), the number of test cases, followed by the input data for each test case. The first line of each test case contains a single integer n (1 <= n <= 100), the number of given strings, followed
by n lines, each representing one string of minimum length 1 and maximum length 100. There is no extra white space before and after a string.
Output
There should be one line per test case containing the length of the largest string found.
Sample Input
2 3 ABCD BCDFF BRCD 2 rose orchid
Sample Output
2 2
题目大意:求出一个最长的串,这个串或者其反向的串是原来所有字符串的子串……
思路:把每一个串和他的反向串连起来(中间用不同的字符隔开),在把所有的串连起来(也用不相同的字符隔开),然后求出其height数组,二分答案,将后缀分组,判断是否有一组中包含了每一个串或者其反转的串~~
// yy实际上是bool数组,判断当前的那个串有没有被用过,通过每次z的值都在变,就省去了的对bool的清零…… //(从论文附件中的标程里学到的orz)
#include <iostream> #include <stdio.h> #include <string> #include <cstring> #define maxn 20201 long t, n, len, z = 0; long yy[101]; long r[maxn], x[maxn], sa[maxn]; long wa[maxn], wb[maxn], ws[maxn], wv[maxn], rank[maxn], height[maxn]; bool cmp (long *r, long a, long b, long l) { return ((r[a] == r[b]) && (r[a + l] == r[b + l])); } void calcsa(long *r, long *sa, long n, long m) { long i, j, p, *x = wa, *y = wb, *t; for (i = 0; i < m; i++) ws[i] = 0; for (i = 0; i < n; i++) ws[x[i] = r[i]]++; for (i = 1; i < m; i++) ws[i] += ws[i - 1]; for (i = n - 1; i >= 0; i--) sa[--ws[x[i]]] = i; for (j = 1, p = 1; p < n; j *= 2, m = p) { for (p = 0, i = n - j; i < n; i++) y[p++] = i; for (i = 0; i < n; i++) if (sa[i] - j >= 0) y[p++] = sa[i] - j; for (i = 0; i < n; i++) wv[i] = x[y[i]]; for (i = 0; i < m; i++) ws[i] = 0; for (i = 0; i < n; i++) ws[wv[i]]++; for (i = 1; i < m; i++) ws[i] += ws[i - 1]; for (i = n - 1; i >= 0;i--) sa[--ws[wv[i]]] = y[i]; t = x; x = y; y = t; p = 1; x[sa[0]] = 0; for (i = 1; i < n ; i++) { x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++; } } } void calcheight(long *r, long *sa, long n) { long i, j, p; for (i = 1; i <= n; i++) rank[sa[i]] = i; p = 0; for (i = 0; i < n; i++) { j = sa[rank[i] - 1]; while (r[i + p] == r[j + p]) p++; height[rank[i]] = p; if (p > 0) p--; } return; } long check (long mid) { long i, j, k, t, s; for (i = 2; i <= len; i = j + 1) { for( ; height[i] < mid && i <= len; i++); for(j = i; height[j] >= mid; j++); if (j - i + 1 < n) continue; s = 0; z++; for (k = i - 1; k < j; k++) { if (((t = x[sa[k]]) != 0) &&(yy[t] != z)) { yy[t] = z; s++; } } if (s >= n) return 1; } return 0; } void deal() { long l = 0, r = 100; while (l <= r) { long mid = (l + r) / 2; if (check(mid)) l = mid + 1; else r = mid - 1; } printf("%d\n", r); } int main() { scanf("%d", &t); while (t--) { scanf("%d", &n); char c[120]; len = 0; for (long i = 1; i <= n; i++) { scanf("%s", c); long k = strlen(c); for (long j = 0; j < k; j++) { r[j + len] = c[j] + 200; x[j + len] = i; } r[len + k] = 2 * i - 1; x[len + k] = 0; len += k + 1; for(long j = 0; j < k; j++) { r[j + len] = c[k - 1 - j] + 200; x[j + len] = i; } r[len + k] = 2 * i; x[len + k] = 0; len += k + 1; } len--; r[len] = 0; if (n == 1) { printf("%d\n", len/ 2); continue; } calcsa(r, sa, len + 1, 400); calcheight(r, sa, len); height[len + 1] = -1; deal(); } return 0 ; }