LuoGu P4391 [BOI2009]Radio Transmission 无线传输

刺骨的言语ヽ痛彻心扉 2023-06-02 11:58 3阅读 0赞

[P4391 \[BOI2009\]Radio Transmission 无线传输][P4391 _BOI2009_Radio Transmission]  
这算是一点\\(next\\)数组的妙用吧...题目要求最小循环节(不要求恰好重复完成).先说结论,答案是\\(n-next\_n\\),为什么呢?  
根据\\(next\\)数组的定义,我们可以知道对于\\(i\\),\\(1\\)到\\(next\_i\\)和\\(next\_\{i-next\_i+1\}\\)到\\(i\\)是相同的,并且并不存在更大的\\(next\\)值满足这个条件.  
所以:当\\(i-next\_i\\)能整除\\(i\\)时,\\(1~i-next\_i\\)就是最小循环节.因为这个题目不要求恰好重复完成,所以不需要判断整除,直接输出即可.  
\\(Code:\\)

#include <algorithm> #include <iostream> #include <cstdlib> #include <cstring> #include <cstdio> #include <string> #include <vector> #include <queue> #include <cmath> #include <ctime> #include <map> #include <set> #define MEM(x,y) memset ( x , y , sizeof ( x ) ) #define rep(i,a,b) for (int i = a ; i <= b ; ++ i) #define per(i,a,b) for (int i = a ; i >= b ; -- i) #define pii pair < int , int > #define X first #define Y second #define rint read<int> #define int long long #define pb push_back using std::set ; using std::pair ; using std::max ; using std::min ; using std::priority_queue ; using std::vector ; using std::swap ; using std::sort ; using std::unique ; using std::greater ; template < class T > inline T read () { T x = 0 , f = 1 ; char ch = getchar () ; while ( ch < '0' || ch > '9' ) { if ( ch == '-' ) f = - 1 ; ch = getchar () ; } while ( ch >= '0' && ch <= '9' ) { x = ( x << 3 ) + ( x << 1 ) + ( ch - 48 ) ; ch = getchar () ; } return f * x ; } template < class T > inline void write (T x) { static T stk[100] , top = 0 ; if ( x == 0 ) { putchar ('0') ; return ; } if ( x < 0 ) { x = - x ; putchar ( '-' ) ; } while ( x ) { stk[++top] = x % 10 ; x /= 10 ; } while ( top ) { putchar ( stk[top--] + '0' ) ; } putchar ('\n') ; } const int N = 1e6 + 100 ; int n , nxt[N] ; char s[N] ; signed main (int argc , char * argv[]) { n = rint () ; scanf ("%s" , s + 1 ) ; int j = 0 ; rep ( i , 2 , n ) { while ( j && s[i] != s[j+1] ) j = nxt[j] ; if ( s[i] == s[j+1] ) ++ j ; nxt[i] = j ; } printf ("%lld\n" , n - nxt[n] ) ; system ("pause") ; return 0 ; }

转载于:https://www.cnblogs.com/Equinox-Flower/p/11480929.html

[P4391 _BOI2009_Radio Transmission]: https://www.luogu.org/problem/P4391