【POJ 2406】 Power Strings

【题目链接】

           点击打开链接

【算法】

         KMP

         如果字符串中存在循环节，则next[len] = (循环节个数 - 1） * 循环节长度

                                                     循环节个数 = len / (len - next[len])

 【代码】

           

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXL 10000010

int len;
char s[MAXL];
int next[MAXL];

template <typename T> inline void read(T &x) {
        int f = 1; x = 0;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
        for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
        x *= f;
}
template <typename T> inline void write(T x) {
    if (x < 0) { putchar('-'); x = -x; }
    if (x > 9) write(x/10);
    putchar(x%10+'0');
}
template <typename T> inline void writeln(T x) {
    write(x);
    puts("");
}

inline void getnext() {
        int i,pos;
        next[1] = 0;
        for (i = 2; i <= len; i++) {
                pos = next[i-1];
                while (pos > 0 && s[pos+1] != s[i]) pos = next[pos];
                if (s[i] == s[pos+1]) next[i] = pos + 1;
                else next[i] = 0;
        }    
}

int main() {
        
        while (true) {
                scanf("%s",s+1);
                if (s[1] == '.') return 0;
                len = strlen(s+1);
                getnext();
                if (len % (len - next[len]) == 0) writeln(len/(len-next[len]));
                else writeln(1);
        }
        
        return 0;
    
}