PAL2_bez stejnych hran

package pal;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    static public int N; //hotels counts = |vertexes|
    static public int M; //track counts = |edges|
    static public int[][] hotels;
    static public int[][] hotelsHelp;
    static public int indexConnection = 0;
    static public boolean notConn = false;
    static public int[] length;

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] in = br.readLine().split(" ");
        N = Integer.parseInt(in[0]);
        M = Integer.parseInt(in[1]);
        length = new int[N];
        hotels = new int[M][3];
        int max = 0;
        int lastUsedLength = 0;
        int helpOldLength = 0;
        int indexLastUsedEdge = 0;
        for (int i = 0; i < M; i++) {
            in = br.readLine().split(" ");
            //x,y,z
            hotels[i][0] = Integer.parseInt(in[0]); //x vertex
            hotels[i][1] = Integer.parseInt(in[1]); //y vertex
            hotels[i][2] = Integer.parseInt(in[2]); //distance between x and y
        }
        //sorted by distance
        hotels = sortArrayByColumn(2);

        for (int i = 0; i < M; i++) {
            //nova delka jina nez posledni nebo jeste nepouzita hrana
            if ((hotels[i][2] != lastUsedLength )|| (length[hotels[i][1]] == 0 && length[hotels[i][0]] == 0)) {
                //s                System.out.println("jina delka " + hotels[i][1] + " " +  hotels[i][0]);
                helpOldLength = length[hotels[i][0]];
                if (helpOldLength < (length[hotels[i][1]] + hotels[i][2])) {
                    lastUsedLength = hotels[i][2];
                    length[hotels[i][0]] = length[hotels[i][1]] + hotels[i][2];

                    if (length[hotels[i][0]] > max) {
                        max = length[hotels[i][0]];
                    }
                }
                if (length[hotels[i][1]] < (helpOldLength + hotels[i][2])) {
                    lastUsedLength = hotels[i][2];
                    length[hotels[i][1]] = helpOldLength + hotels[i][2];
                    if (length[hotels[i][1]] > max) {
                        max = length[hotels[i][1]];
                    }
                }
            } else { //stejna delka jako posledni

                //hrana se stejnou delkou nesousedi s posledni hranou se stejnou delkou
                if ((hotels[i][1] != hotels[indexLastUsedEdge][1] && hotels[i][1] != hotels[indexLastUsedEdge][0])
                        && (hotels[i][0] != hotels[indexLastUsedEdge][1] && hotels[i][0] != hotels[indexLastUsedEdge][0])) {
                    //          System.out.println("stejna dalka, hrana pouzita " + hotels[i][1] + " " +  hotels[i][0]);
                }
            }
        }
        System.out.println(max);
    }

    public static int[][] sortArrayByColumn(int column) {
        int[][] sortedArray = new int[M][3];
        int min = hotels[0][column];
        int max = hotels[0][column];
        //find min and max values for histogram from current column
        for (int i = 1; i < M; i++) {
            if (hotels[i][column] < min) {
                min = hotels[i][column];
            } else if (hotels[i][column] > max) {
                max = hotels[i][column];
            }
        }
        //histogram length from min to max
        int[] hist = new int[max - min + 1];
        for (int i = 0; i < M; i++) {
            hist[hotels[i][column] - min]++;
        }
        //pole vyskytu
        hist[0]--;
        for (int i = 1; i < hist.length; i++) {
            hist[i] = hist[i] + hist[i - 1];
        }
        //min to max
        for (int i = M - 1; i >= 0; i--) {
            int histIndex = hotels[i][column] - min;
            int index = hist[histIndex];
            sortedArray[index][column] = hotels[i][column];
            sortedArray[index][1] = hotels[i][1];
            sortedArray[index][0] = hotels[i][0];
            hist[histIndex]--;
        }
        return sortedArray;
    }
}