Poj2406 KMP Algorithm

Poj2406

Restatement: Given the string S0, record the s0s0 .. S0 consisting of consecutive k s and connected to S0 ^ K. Input the string s to obtain the maximum K so that S = S0 ^ K.

Problem Analysis:

1. Use the KMP algorithm to obtain the prefix function prefix [I] (I = 1, 2,... n, n = length (s )).

2. If n-Prefix [N] can be divisible by N, S can be expressed as K = N/(n-Prefix [N]) consecutive S0, and K obtains the maximum value at this time.

3. Otherwise, s cannot be expressed as a continuous S0, k = 1.

AC code:

 1 //Memory: 5680K        Time: 313MS 2 #include <iostream> 3 #include <cstring> 4 #include <string> 5  6 using namespace std; 7  8 const int maxn = 1000010; 9 10 int prefix[maxn];11 string s;12 13 void init()14 {15     int l = s.size();16     memset(prefix, 0, sizeof(prefix));17     int k = 0;18     for (int i = 2; i <= l; i++) {19         while (k > 0 && s[k] != s[i - 1])20             k = prefix[k];21         if (s[k] == s[i - 1])22             k++;23         prefix[i] = k;24     }25 }26 27 int main()28 {29     while (cin >> s && s != ".") {30         init();31         int l = s.size();32         33         if ( prefix[l] != 0 && l % (l - prefix[l]) == 0) 34             cout << l / (l - prefix[l]) << endl;35         else36             cout << "1" << endl;37     }38     return 0;39 }

 

Poj2406 KMP Algorithm