后缀数组+RMQ。
1 /* 2459 */
2 #include <iostream>
3 #include <sstream>
4 #include <string>
5 #include <map>
6 #include <queue>
7 #include <set>
8 #include <stack>
9 #include <vector>
10 #include <deque>
11 #include <algorithm>
12 #include <cstdio>
13 #include <cmath>
14 #include <ctime>
15 #include <cstring>
16 #include <climits>
17 #include <cctype>
18 #include <cassert>
19 #include <functional>
20 #include <iterator>
21 #include <iomanip>
22 using namespace std;
23 //#pragma comment(linker,"/STACK:102400000,1024000")
24
25 #define sti set<int>
26 #define stpii set<pair<int, int> >
27 #define mpii map<int,int>
28 #define vi vector<int>
29 #define pii pair<int,int>
30 #define vpii vector<pair<int,int> >
31 #define rep(i, a, n) for (int i=a;i<n;++i)
32 #define per(i, a, n) for (int i=n-1;i>=a;--i)
33 #define clr clear
34 #define pb push_back
35 #define mp make_pair
36 #define fir first
37 #define sec second
38 #define all(x) (x).begin(),(x).end()
39 #define SZ(x) ((int)(x).size())
40 #define lson l, mid, rt<<1
41 #define rson mid+1, r, rt<<1|1
42
43 const int INF = 0x3f3f3f3f;
44 const int maxn = 1e5+5;
45 char s[maxn];
46 int a[maxn];
47 int rrank[maxn], height[maxn], sa[maxn];
48 int wa[maxn], wb[maxn], wc[maxn], wv[maxn];
49 int dp[maxn][17];
50 int mx[maxn], L[maxn];
51
52 bool cmp(int *r, int a, int b, int l) {
53 return r[a]==r[b] && r[a+l]==r[b+l];
54 }
55
56 void da(int *r, int *sa, int n, int m) {
57 int i, j, *x=wa, *y=wb, *t, p;
58
59 for (i=0; i<m; ++i) wc[i] = 0;
60 for (i=0; i<n; ++i) wc[x[i]=r[i]]++;
61 for (i=1; i<m; ++i) wc[i] += wc[i-1];
62 for (i=n-1; i>=0; --i) sa[--wc[x[i]]] = i;
63 for (j=1,p=1; p<n; j*=2, m=p) {
64 for (p=0,i=n-j; i<n; ++i) y[p++] = i;
65 for (i=0; i<n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
66 for (i=0; i<n; ++i) wv[i] = x[y[i]];
67 for (i=0; i<m; ++i) wc[i] = 0;
68 for (i=0; i<n; ++i) wc[x[i]]++;
69 for (i=1; i<m; ++i) wc[i] += wc[i-1];
70 for (i=n-1; i>=0; --i) sa[--wc[wv[i]]] = y[i];
71 for (t=x, x=y, y=t, p=1, i=1, x[sa[0]]=0; i<n; ++i)
72 x[sa[i]] = cmp(y, sa[i-1], sa[i], j) ? p-1 : p++;
73 }
74 }
75
76 void calheight(int *r, int *sa, int n) {
77 int i, j, k = 0;
78
79 for (i=1; i<=n; ++i) rrank[sa[i]] = i;
80 for (i=0; i<n; height[rrank[i++]]=k)
81 for (k?k--:0, j=sa[rrank[i]-1]; r[j+k]==r[i+k]; ++k) ;
82 }
83
84 void init_RMQ(int n) {
85 int i, j;
86
87 for (i=1; i<=n; ++i)
88 dp[i][0] = height[i];
89 dp[1][0] = INF;
90 for (j=1; (1<<j)<=n; ++j)
91 for (i=1; i+(1<<j)-1<=n; ++i)
92 dp[i][j] = min(dp[i][j-1], dp[i+(1<<(j-1))][j-1]);
93 }
94
95 int RMQ(int l, int r) {
96 if (l > r)
97 swap(l, r);
98
99 int k = 0;
100 ++l;
101 while (1<<(k+1) <= r-l+1)
102 ++k;
103
104 return min(dp[l][k], dp[r-(1<<k)+1][k]);
105 }
106
107 void printSa(int n) {
108 for (int i=1; i<=n; ++i)
109 printf("%d ", sa[i]);
110 putchar(‘\n‘);
111 }
112
113 void printHeight(int n) {
114 for (int i=1; i<=n; ++i)
115 printf("%d ", height[i]);
116 putchar(‘\n‘);
117 }
118
119 void solve() {
120 int n;
121
122 for (int i=0; ; ++i) {
123 if (s[i] == ‘\0‘) {
124 n = i;
125 break;
126 }
127 a[i] = s[i] - ‘a‘ + 1;
128 }
129 a[n] = 0;
130
131 da(a, sa, n+1, 30);
132 calheight(a, sa, n);
133 init_RMQ(n);
134
135 int n_ = n >> 1, tmp;
136 rep(i, 1, n_) {
137 mx[i] = 0;
138 for (int p=0, q=i; q<n; p=q, q+=i) {
139 tmp = RMQ(rrank[p], rrank[q]);
140 mx[i] = max(mx[i], tmp/i+1);
141 if (tmp%i) {
142 tmp = RMQ(rrank[p-(i-tmp%i)], rrank[q-(i-tmp%i)]);
143 mx[i] = max(mx[i], tmp/i+1);
144 }
145 }
146 }
147
148 int ans = 0;
149 rep(i, 1, n_)
150 ans = max(ans, mx[i]);
151
152 int ln = 0;
153 rep(i, 1, n_) {
154 if (mx[i] == ans) {
155 L[ln++] = i;
156 }
157 }
158
159 int beg = 0, len = 0;
160
161 rep(i, 1, n+1) {
162 rep(j, 0, ln) {
163 int p = sa[i];
164 if (p+L[j] >= n)
165 continue;
166
167 tmp = RMQ(rrank[p], rrank[p+L[j]]);
168 if (tmp/L[j]+1 >= ans) {
169 beg = p;
170 len = L[j] * ans;
171 goto _output;
172 }
173 }
174 }
175
176 _output:
177 s[beg+len] = ‘\0‘;
178 puts(s+beg);
179 }
180
181 int main() {
182 ios::sync_with_stdio(false);
183 #ifndef ONLINE_JUDGE
184 freopen("data.in", "r", stdin);
185 freopen("data.out", "w", stdout);
186 #endif
187
188 int t = 0;
189
190 while (scanf("%s", s)!=EOF && (s[0]!=‘#‘)) {
191 printf("Case %d: ", ++t);
192 solve();
193 }
194
195 #ifndef ONLINE_JUDGE
196 printf("time = %d.\n", (int)clock());
197 #endif
198
199 return 0;
200 }
数据生成器。
1 from random import randint, shuffle
2 import shutil
3 import string
4
5
6 def GenDataIn():
7 with open("data.in", "w") as fout:
8 t = 20
9 bound = 10**2
10 lc = list(string.lowercase)
11 for tt in xrange(t):
12 length = randint(100, 500)
13 line = ""
14 for i in xrange(length):
15 idx = randint(0, 25)
16 line += lc[idx]
17 fout.write("%s\n" % line)
18 fout.write("#\n")
19
20
21 def MovDataIn():
22 desFileName = "F:\eclipse_prj\workspace\hdoj\data.in"
23 shutil.copyfile("data.in", desFileName)
24
25
26 if __name__ == "__main__":
27 GenDataIn()
28 MovDataIn()
时间： 2024-10-13 01:04:53