CF615C Running Track

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 #include <vector>
 5 using namespace std;
 6 const int MAXN = 2105;
 7 int neXt[MAXN];
 8 
 9 void getNext(string s)
10 {
11     int n = s.length();
12     neXt[0] = -1;
13     int k = -1, j = 0;
14     while (j < n)
15     {
16         if (k == -1 || s[j] == s[k])
17         {
18             j++; k++;
19             if (s[j] != s[k]) neXt[j] = k;
20             else neXt[j] = neXt[k];
21         }
22         else
23         {
24             k = neXt[k];
25         }
26     }
27 }
28 
29 int kmp(string s, string p)
30 {
31     int i = 0, j = 0;
32     int m = s.length(), n = p.length();
33     while (i < m && j < n)
34     {
35         if (j == -1 || s[i] == p[j]) i++, j++;
36         else j = neXt[j];
37     }
38     if (j == n) return i - j;
39     return -1;
40 }
41 
42 bool solve(string x, string y, vector<pair<int, int>> & ans)
43 {
44     string z(x);
45     reverse(z.begin(), z.end());
46     int m = x.length();
47     int n = y.length();
48     int start = 0;
49     while (start < n)
50     {
51         int l = 1, r = n - start, res = 0, pos = -1;
52         bool flg = true;
53         while (l <= r)
54         {
55             int mid = (l + r) >> 1;
56             string tmp = y.substr(start, mid);
57             getNext(tmp);
58             int p = kmp(x, tmp);
59             if (p != -1)
60             {
61                 res = mid; pos = p; flg = true; l = mid + 1;
62             }
63             else if ((p = kmp(z, tmp)) != -1)
64             {
65                 res = mid; pos = p; flg = false; l = mid + 1;
66             }
67             else r = mid - 1;
68         }
69         if (!res) return false;
70         if (flg) ans.push_back(pair<int, int>(pos + 1, pos + res));
71         else ans.push_back(pair<int, int>(m - pos, m - pos - res + 1));
72         start += res;
73     }
74     return true;
75 }
76     
77 int main()
78 {
79     string x, y;
80     cin >> x >> y;
81     vector<pair<int, int>> res;
82     if (solve(x, y, res))
83     {
84         cout << res.size() << endl;
85         for (int i = 0; i < res.size(); i++)
86             cout << res[i].first << " " << res[i].second << endl;
87     }
88     else
89     {
90         puts("-1");
91     }
92     return 0;
93 }