알고스팟 자바(java) 해답 : DARPA

import java.util.*;

public class Main {
	static int n,m,seen;
	static double result;
	static double []location;
	static double [][]length;
	public static void main(String args[]){

		location = new double[200];
		length = new double[200][200];

		Scanner scanner = new Scanner(System.in);

		int testcase = scanner.nextInt();

		for(int i = 0; i < testcase; i++){
			result = 0;
			n = scanner.nextInt();
			m = scanner.nextInt();
			for(int j = 0; j < m; j++){
				location[j] = scanner.nextDouble();
			}
			for(int k = 0; k < m-1; k++){
				for(int l = k + 1; l < m; l++){
					calculate(k,l);
				}
			}
			result = optimize();
			System.out.printf("%.2f\n", result);
		}
	}
	public static void calculate(int k, int l){
		double temp = location[l] - location[k];
		length[l][k] = temp;
		length[k][l] = temp;
	}
	public static double optimize(){
		double lo = 0; 
		double hi = 240;
		double mid;
		for(int i = 0; i < 20; i++){
			mid = (lo + hi) / 2; 
			if(decision(mid)){
				lo = mid;
			}
			else
				hi = mid;
		}
		return hi;
	}
	public static Boolean decision(double mid){
		int now;
		Boolean result;
		for(int i = 0; i < m-1; i++){
			seen = 1;
			now = i;
			result = nextvalue(now, mid);
			if(result == true)
				return true;
		}
		return false;
	}
	public static Boolean nextvalue(int a, double mid){
		Boolean result;
		for(int i = a + 1; i < m; i++){
			if(length[a][i] >= mid){
				seen++;
				if(seen == n)
					return true;
				result = nextvalue(i, mid);
				if(result == true)
					return true;
				break;
			}
		}
		return false;
	}
}