Power Strings(POJ2406)(KMP)
阿新 • • 發佈:2018-12-24
Power Strings
Each test case is a line of input representing s, a string of printable characters. The length of s will be at least 1 and will not exceed 1 million characters. A line containing a period follows the last test case.
第j位不匹配則要回到第next[i]位繼續與文字串第j位匹配。
則模式串第1位到next[n]與模式串第n-next[n]位到n位是匹配的。
如果n%(n-next[n])==0,則存在重複連續子串,長度為n-next[n]。
Time Limit: 3000MS | Memory Limit: 65536K |
Total Submissions: 33623 | Accepted: 13966 |
Description
Given two strings a and b we define a*b to be their concatenation. For example, if a = "abc" and b = "def" then a*b = "abcdef". If we think of concatenation as multiplication, exponentiation by a non-negative integer is defined in the normal way: a^0 = "" (the empty string) and a^(n+1) = a*(a^n).Input
Output
For each s you should print the largest n such that s = a^n for some string a.Sample Input
abcd aaaa ababab .
Sample Output
1 4 3
Hint
This problem has huge input, use scanf instead of cin to avoid time limit exceed.Source
KMP,next表示模式串如果第i位(設str[0]為第0位)與文字串第j位不匹配則要回到第next[i]位繼續與文字串第j位匹配。
則模式串第1位到next[n]與模式串第n-next[n]位到n位是匹配的。
如果n%(n-next[n])==0,則存在重複連續子串,長度為n-next[n]。
#include<stdio.h> #include<string.h> #include<algorithm> using namespace std; int next[1000002]; char s[1000002]; int len; int get_next(char *s) { int i=0,j=-1; next[0]=-1; while(i<len) { if(j==-1||s[i]==s[j]) { i++; j++; next[i]=j; } else j=next[j]; } if(len%(len-next[len])==0) return len/(len-next[len]); else return 1; } int main() { while(gets(s)!=NULL) { if(s[0]=='.') break; len=strlen(s); printf("%d\n",get_next(s)); } return 0; }