poj2406--Power Strings(KMP求最小迴圈節)
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.
Time Limit:3000MS | Memory Limit:65536K |
Total Submissions:33178 | Accepted:13792 |
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
Waterloo local 2002.07.01用next陣列求出整個陣列的最大字首,如果整個串是用迴圈節組成的,那麼 n - next[n] 也就是最小迴圈節,驗證最小迴圈節會被n整出。
#include <cstdio> #include <cstring> #include <algorithm> int next[1100000] ; char str[1100000] ; void getnext(int l) { int j = 0 , k = -1 ; next[0] = -1 ; while(j < l) { if( k == -1 || str[j] == str[k] ) { j++ ; k++ ; next[j] = k ; } else k = next[k] ; } } int main() { int l , m ; while(scanf("%s", str)!=EOF) { if( str[0] == '.' ) break; l = strlen(str); getnext(l) ; m = next[l]; if( l % (l-m) != 0 ) printf("1\n"); else { m = l / ( l-m ); printf("%d\n", m); } memset(str,0,sizeof(str)); } return 0; }