PAL2-23-10

package pal;

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

/**
 *
 * @author Alisa
 */
public class Main {

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

    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]);
        vertexes = new int[N][4]; //aktualni delka do vrcholu, delka posledni hrany vstoupivsi do vrcholu, delka predchozich hrany
        //////////////DADA KOMENT//////////////
        //takze
        //0-aktualni delka
        //1-posledni vstupujici hrana
        //2-posledni velikost kterou dovezla hrana s delkou ktera se rovna akrualni nejvetsi hrane ktera do uzlu vstoupila
        //3-nejvetsi vzdalenost kterou do uzlu dovezla hrana mensi nez nejvetsi ktera do uzlu vstupuje
        //////////////DADA KOMENT//////////////

        edges = new int[M][3]; //vrchol A, vrchol B, delka hrany AB
        int max = 0;
        for (int i = 0; i < M; i++) {
            in = br.readLine().split(" ");
            //x,y,z
            edges[i][0] = Integer.parseInt(in[0]) - 1; //x vertex
            edges[i][1] = Integer.parseInt(in[1]) - 1; //y vertex
            edges[i][2] = Integer.parseInt(in[2]); //distance between x and y
        }
        //sorted by distance
        edges = sortArrayByColumn(2);
        for (int i = 0; i < M; i++) {
            int bodA = edges[i][0];
            int bodB = edges[i][1];
            int delkaNoveHrany = edges[i][2];
            int maxDelkaA = vertexes[bodA][0];
            int maxDelkaB = vertexes[bodB][0];
            int delkaSoucHranyA = vertexes[bodA][1];
            int delkaSoucHranyB = vertexes[bodB][1];
            int delkaMinuleHranyA = vertexes[bodA][2];
            int delkaMinuleHranyB = vertexes[bodB][2];

            //predchozi hrana vrcholu A == soucasna hrana && predchozi hrana vrcholu B == soucasna hrana
            if (vertexes[edges[i][0]][1] == edges[i][2] && vertexes[edges[i][1]][1] == edges[i][2]) {   //delka do vrcholu A nebo B mensi jak nova hrana -> nahradime ji
                if (vertexes[edges[i][0]][0] < edges[i][2]) {
                    //////////////DADA KOMENT//////////////
                    //rika ze pokud stejne velka hrana edges[i][2] doveze vetsi vzdalenost(vzdalenost kterou do protejsiho uzlu dovezla hrana mensi nez edges[i][2]) do uzlu vertexes[edges[i][0]][2], zmeni se hodnota dovezena hranou edges[i][2] na danou hodnotu
                    if (vertexes[edges[i][0]][2] < vertexes[edges[i][1]][3] + edges[i][2]) {
                        vertexes[edges[i][0]][2] = vertexes[edges[i][1]][3] + edges[i][2];
                    }
                    //tohle v blede modrym o par radek niz a pro radky 120,140
                    //////////////DADA KOMENT//////////////

                    //////////////DADA KOMENT//////////////
                    //pricist hodnotu vertexes[edges[i][1]][3], protoze to je hodnota soucasne hrany + hodnota kterou do protejsi odvezla hrana s mensi velikosti
                    //opet v blede modrem o par radek niz a vsude kde do vertexes[cokoli][0] davas jen edges[i][2]
                    vertexes[edges[i][0]][0] = edges[i][2] + vertexes[edges[i][1]][3];
                    //////////////DADA KOMENT//////////////
                    if (edges[i][2] > max) {
                        max = edges[i][2];
                    }
                }
                if (vertexes[edges[i][1]][0] < edges[i][2] + vertexes[edges[i][0]][3]) {
                    vertexes[edges[i][1]][0] = edges[i][2] + vertexes[edges[i][0]][3];
                    if (edges[i][2] > max) {
                        max = edges[i][2];
                    }
                }
                continue;
            }
            //predchozi hrana vrcholu A a B != soucasna hrana
            if (vertexes[edges[i][0]][1] != edges[i][2] && vertexes[edges[i][1]][1] != edges[i][2]) {
                int help = vertexes[edges[i][0]][0];
                //delka ve vrcholu A < nez B + nova cesta
                if (help < (vertexes[edges[i][1]][0] + edges[i][2])) {

                    //////////////DADA KOMENT//////////////
                    //tady vstupuje na radu vetsi hrana nez tak byla tudiz je potreba se podivat jestli se nemeni nejvesti privedena velikost hranou mensi nez aktualni
                    if (vertexes[edges[i][0]][3] < vertexes[edges[i][0]][2]) {
                        vertexes[edges[i][0]][3] = vertexes[edges[i][0]][2];
                    }
                    //nastavi velikost privedene cesty, aktualni cestou
                    vertexes[edges[i][0]][2] = vertexes[edges[i][0]][1] + edges[i][2];
                    //to same v blede modrem o par radku dal a na radkach 114,133
                    //////////////DADA KOMENT//////////////

                    vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = vertexes[edges[i][1]][0] + edges[i][2];
                    if (vertexes[edges[i][0]][0] > max) {
                        max = vertexes[edges[i][0]][0];
                    }
                }
                //delka ve vrcholu B < nez A + nova cesta
                if (vertexes[edges[i][1]][0] < (help + edges[i][2])) {
                    vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = help + edges[i][2];
                       vertexes[edges[i][1]][2] = vertexes[edges[i][1]][1] + edges[i][2];

                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
                continue;
            }
            //predchozi hrana vrcholu A == soucasna hrana
            if (vertexes[edges[i][0]][1] == edges[i][2]) {
                int help = vertexes[edges[i][1]][0];
                if (help < edges[i][2]  + vertexes[edges[i][0]][3]) {
                    vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = edges[i][2] +  + vertexes[edges[i][0]][3];
                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
                if (help + edges[i][2] > vertexes[edges[i][0]][0]) {
                    vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = help + edges[i][2];
                       vertexes[edges[i][0]][2] = vertexes[edges[i][0]][1] + edges[i][2];

                    if (vertexes[edges[i][0]][0] > max) {
                        max = vertexes[edges[i][0]][0];
                    }
                }
                continue;
            }
            //predchozi hrana vrcholu B == soucasna hrana
            if (vertexes[edges[i][1]][1] == edges[i][2]) {
                int help = vertexes[edges[i][0]][0];
                if (help < edges[i][2] + vertexes[edges[i][1]][3]) {
                    vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = edges[i][2] + vertexes[edges[i][1]][3];
                        max = vertexes[edges[i][0]][0];
                    }

                if (help + edges[i][2] > vertexes[edges[i][1]][0]) {
                    vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = help + edges[i][2];
                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
            }
        }
        System.out.println(max);
    }
    public static int[][] sortArrayByColumn(int column) {
        int[][] sortedArray = new int[M][3];
        int min = edges[0][column];
        int max = edges[0][column];
        //find min and max values for histogram from current column
        for (int i = 1; i < M; i++) {
            if (edges[i][column] < min) {
                min = edges[i][column];
            } else if (edges[i][column] > max) {
                max = edges[i][column];
            }
        }
        //histogram length from min to max
        int[] hist = new int[max - min + 1];
        for (int i = 0; i < M; i++) {
            hist[edges[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 = edges[i][column] - min;
            int index = hist[histIndex];
            sortedArray[index][column] = edges[i][column];
            sortedArray[index][1] = edges[i][1];
            sortedArray[index][0] = edges[i][0];
            hist[histIndex]--;
        }
        return sortedArray;
    }

}