图 --- 二分图

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

const int MAX = 100;
vector<int> G[MAX];

/**
    struct edge{
        int to;
        int cost;
    };
    vector<edge> G[MAX];
*/
int main()
{
    int V,E;
    cin>>V>>E;
    for(int i=0;i<V;i++){
        int s,t;
        cin>>s>>t;
        G[s].push_back(t);
    }
    ...
}

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

const int MAX = 100;
vector<int> G[MAX];
int V;
int color[MAX];

bool dfs(int v,int c){
    color[v] = c;
    for(unsigned int i=0;i<G[v].size();i++){
        if(color[G[v][i]] == c) return false;
        if(color[G[v][i]]==0 && !dfs(G[v][i],-c)) return false;
    }
    return true;
}
void slove(){
    for(int i=0;i<V;i++){
        if(color[i]==0){
            if(!dfs(i,1)){
                cout<<"No"<<endl;
                return;
            }
        }
    }
    cout<<"Yes"<<endl;
}
int main()
{
    cin>>V;
    for(int i=0;i<V;i++){
        int s,t;
        cin>>s>>t;
        G[s].push_back(t);
        G[t].push_back(s);
    }
    slove();
}