21-算法训练 字串统计

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner cin = new Scanner(System.in);
		String[] str = new String[3800];
		int n = cin.nextInt();
		String yuan = cin.next(); 
		int len = yuan.length();
		int ct = 0;
		for(int i = 0; i < len; i++) {
			for(int j = i; j < len; j++) { // i 和 j 的关系
				str[ct++] = yuan.substring(i, j+1);
			}
		}
		int[] cishu = new int[ct];
		//哦统计
		for(int i = 0; i < ct; i++) {
			for(int j = 0; j < ct; j++) {
				if(i != j && str[i].equals(str[j])) {
					cishu[i]++;
				}
			}
		}
		int max = 0;
		String ans = ""; //最长的串
		for(int i = 0; i < ct; i++) {
			if(str[i].length() >= n) {
				if(cishu[i] > max) {
					max = cishu[i];
					ans = str[i];
				}
				else if(cishu[i] == max) {
					if(str[i].length() > ans.length()) {
						max = cishu[i];
						ans = str[i];
					}
				}
			}
		}
		if(ans.length() == 0) {
			
		}
		else {
			System.out.println(ans);
		}
	}
}
//4
//bbaabbaaaaa