HDU 3294 (Manacher) Girls' research

 1 //#define LOCAL
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 const int maxn = 200000 + 20;
 8 char s1[maxn], s2[maxn * 2], real;
 9 int p[maxn * 2];
10 
11 void init(char s1[], char s2[])
12 {
13     int j = 2;
14     s2[0] = ‘$‘, s2[1] = ‘#‘;
15     for(int i = 0; s1[i] != ‘\0‘; ++i)
16     {
17         s2[j++] = s1[i];
18         s2[j++] = ‘#‘;
19     }
20     s2[j] = ‘\0‘;
21 }
22 
23 void manacher(char s[])
24 {
25     p[0] = 0;
26     int id, mx = 0;
27     for(int i = 1; s[i] != ‘\0‘; ++i)
28     {
29         if(mx > i)
30             p[i] = min(p[id*2-i], mx-i);
31         else
32             p[i] = 1;
33         while(s[i + p[i]] == s[i - p[i]])
34             ++p[i];
35         if(i + p[i] > mx)
36         {
37             id = i;
38             mx = i + p[i];
39         }
40     }
41 }
42 
43 char change(char c)
44 {
45     c -= real - ‘a‘;
46     if(c < ‘a‘)    c += 26;
47     if(c > ‘z‘)    c -= 26;
48     return c;
49 }
50 
51 void getans(void)
52 {
53     int mlen = 1, pos;
54     for(int i = 1; s2[i] != ‘\0‘; ++i)
55     {
56         if(p[i] - 1 > mlen)
57         {
58             mlen = p[i] - 1;
59             pos = i;
60         }
61     }
62     if(mlen == 1)
63         printf("No solution!\n");
64     else
65     {
66         int L = (pos - (p[pos] - 2)) / 2 - 1;
67         int R = (pos + (p[pos] - 2)) / 2 - 1;
68         printf("%d %d\n", L, R);
69         for(int i = L; i <= R; ++i)
70             printf("%c", change(s1[i]));
71         printf("\n");
72     }
73 }
74 
75 int main(void)
76 {
77     #ifdef LOCAL
78         freopen("3294in.txt", "r", stdin);
79     #endif
80 
81     
82     while(scanf("%c", &real) == 1)
83     {
84         scanf("%s", s1);
85         getchar();
86         init(s1, s2);
87         manacher(s2);
88         getans();
89     }
90     return 0;
91 }