KMP中next数组求解

字符串从1开始

for(int i = 2,j = 0; i <= n; i ++) {
    
    
        		while(j != 0 && s[i] != s[j+1] ) j = ne[j];
        		if(s[i] == s[j+1]) j++;
        		ne[i] = j;
        	}

例题：
141. 周期

import java.io.*;
import java.util.*;
public class Main {
    
    
	static int N = 1000010;
	static int []ne = new int [N];
    public static void main(String[] args) throws IOException {
    
    
        Scanner sc = new Scanner(System.in);
        int n,t=0;
        while((n = sc.nextInt())!=0) {
    
    
        	char []s = (" "+ sc.next()).toCharArray();
        	for(int i = 2,j = 0; i <= n; i ++) {
    
    
        		while(j != 0 && s[i] != s[j+1] ) j = ne[j];
        		if(s[i] == s[j+1]) j++;
        		ne[i] = j;
        	}
        	System.out.println("Test case #" + ++t);
        	for(int i = 2; i <= n; i ++) {
    
    
        		int k = i -ne[i];
        		if(i % k == 0 && i / k > 1)
        			System.out.println(i +" " + i / k);
        	}
        	System.out.println();
        }
    	sc.close();
    }
}