Graph painting

#include <bits/stdc++.h>
using namespace std;
#define int long long

string to_string(string s) {
    return '"' + s + '"';
}
 
string to_string(const char* s) {
    return to_string((string) s);
}
 
string to_string(bool b) {
    return (b ? "true" : "false");
}
 
template <typename A, typename B>
string to_string(pair<A, B> p) {
    return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
 
template <typename A>
string to_string(A v) {
    bool first = true;
    string res = "{";
    for (const auto &x : v) {
        if (!first) {
            res += ", ";
        }
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}
 
void debug_out() {
    cerr << endl;
}
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << to_string(H);
    debug_out(T...);
}
 
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

const int N = 1e5 + 5;
const int M = 2e5 + 5;

int n, m;
vector<int> adj[N];
int deg[N];
int col[N];

void dfs(int u, int c) {
    col[u] = c;
    for (int v : adj[u]) {
        if (col[v] == -1) {
            dfs(v, 1 - c);
        }
    }
}

void solve() {
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        deg[u]++;
        deg[v]++;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    vector<int> order(n);
    for (int i = 1; i <= n; i++) {
        order[i - 1] = i;
    }
    sort(order.begin(), order.end(), [&](int i, int j){
        return deg[i] > deg[j];
    });

    for (int u : order) {
        if (col[u] == -1) {
            dfs(u, 1);
        }
    }

    for (int i = 1; i <= n; i++) {
        cout << (col[i] ? "R" : "B") << ' ';
    }
    cout << '\n';
}

void clean() {
    for (int i = 1; i <= n; i++) {
        adj[i].clear();
        col[i] = -1;
        deg[i] = 0;
    }
}

signed main() {
    cin.tie(0)->sync_with_stdio(0);

    memset(col, -1, sizeof col);
    memset(deg, 0, sizeof deg);

    int t;
    cin >> t;

    while (t--) {
        solve();
        clean();
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED