i'm stuck with this problem for about 2 hours and still wa44. Any advices?
Here is my code:
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>
#include<set>
#include <fstream>
#include <iomanip>
#include <list>
#include <stack>
#include <map>
#include <math.h>
#include <unordered_map>

using namespace std;

vector<vector<int>> edges;

vector<bool> used;

void dfs(int from)
{
    if (!used[from])
    {
        used[from] = true;
        for (auto a : edges[from])
            dfs(a);
    }
}

vector<bool> colours;
bool coloringDfs(int from, bool color)
{
    if (used[from])
    {

    }
    else
    {
        used[from] = true;
        colours[from] = color;
        for (auto a : edges[from])
            if (used[a])
            {
                if (colours[a] == color)
                    return false;
            }
            else
            if(!coloringDfs(a, !color)) return false;
        return true;
    }
}

vector<int> meanings;

bool coloringDfs2(int from, bool color, int min)
{
    if (used[from])
    {

    }
    else
    {
        used[from] = true;
        meanings[from] = color+1+min;
        for (auto a : edges[from])
            if (!coloringDfs2(a, !color,min)) return false;
        return true;
    }
}

int bfs(int from, int n)
{
    vector<bool> us = vector<bool>(n, false);
    int currentLevel = 1;
    vector<int> v1;
    v1.push_back(from);
    us[from] = true;
    vector<int> v2;
    while (v1.size())
    {
        for(auto a:v1)
            for(auto b: edges[a])
                if (!us[b])
                {
                    us[b] = true;
                    v2.push_back(b);
                }
        currentLevel++;
        swap(v1, v2);
        v2.clear();
    }

    return currentLevel-2;

}

int bfs2(int from, int n)
{
    vector<bool> us = vector<bool>(n, false);
    int currentLevel = 1;
    vector<int> v1;
    v1.push_back(from);
    meanings[from] = 1;
    us[from] = true;
    vector<int> v2;
    while (v1.size())
    {
        for (auto a : v1)
            for (auto b : edges[a])
                if (!us[b])
                {
                    us[b] = true;
                    meanings[b] = currentLevel + 1;
                    v2.push_back(b);
                }
        currentLevel++;
        swap(v1, v2);
        v2.clear();
    }

    return currentLevel-1;

}


int main()
{
    int m;
    int n;
    cin >> m >> n;
    used = vector<bool>(n,false);
    edges = vector<vector<int>>(n, vector<int>());
    for (int i = 0; i < m; ++i)
    {
        int x, y;
        cin >> x >> y;
        --x;
        --y;
        edges[x].push_back(y);
        edges[y].push_back(x);
    }

    colours = vector<bool>(n);
    for (int i = 0; i < n; ++i)
    {
        used = vector<bool>(n, false);

        if (!coloringDfs(0, 0))
        {
            cout << -1; return 0;
        }
    }


    dfs(0);
    meanings = vector<int>(n);
    for(int i = 0 ; i < n; ++i)
        if (!used[i])
        {
            cout << 49;
            used = vector<bool>(n, false);
            meanings = vector<int>(n, 0);
            bool ok = false;
            for(int i = 0 ; i < n; ++i)
                if (!used[i])
                {
                    coloringDfs2(i, ok, 48 * ok);
                    ok = !ok;
                }
            cout << endl;
            for (auto a : meanings)
                cout << a << " ";
            return 0;
        }
    int currentMax = bfs(0, n);
    int currentIndex = 0;
    for (int i = 1; i < n; ++i)
    {
        int x = bfs(i, n);
        if (x > currentMax)
        {
            currentMax = x;
            currentIndex = i;
        }
    }
    bfs2(currentIndex, n);
    cout << currentMax << endl;
    for (auto a : meanings)
        cout << a<<" ";



}