백준 1707번 C++ 풀이

#include <iostream>
#include <queue>
#include <vector>
using namespace std;

int isVisited[20001];
vector<int> buffer[20001];
int main() {
    cin.tie(NULL);
    ios::sync_with_stdio(false);
    int t;
    cin >> t;
    for (auto z=0; z<t; z++){
        int v, e;
        cin >> v >> e;

        for (auto i = 1; i<=v; i++){
            isVisited[i] = 0;
            buffer[i].clear();
        }
        for (auto i = 0; i<e; i++){
            int to, from;
            cin >> to >> from;
            buffer[to].push_back(from);
            buffer[from].push_back(to);
        }

        bool isBipartite = true;
        for (auto i=1; i<=v; i++){
            if (isVisited[i] == 0){
                isVisited[i] = 1;
                queue<pair<int, int>> q;
                q.push(make_pair(i, 1));
                while (!q.empty()){
                    auto top = q.front();
                    q.pop();
                    for (auto edge : buffer[top.first]){
                        if (isVisited[edge] == 0){
                            isVisited[edge] = 3 - top.second;
                            q.push(make_pair(edge, isVisited[edge]));
                        }
                    }
                }
            }
        }
        for (auto i = 1; i<=v; i++){
            int top = isVisited[i];
            for (auto edge : buffer[i]){
                if (isVisited[edge] == top){
                    isBipartite = false;
                }
            }
        }
        if (isBipartite){
            cout << "YES";
        }else {
            cout << "NO";
        }
        cout << '\n';

    }
    return 0;

}