样例2没过，提交AC

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556#include <bits/stdc++.h>
using namespace std;
#define Code ios::sync_with_stdio(0);
#define by cin.tie(0);
#define Eric cout.tie(0);
#define inf 0x3f3f3f3f
#define linf 0x3f3f3f3f3f3f3f3f
vector<int> e[1005];
int c[1005];
bool g[1005][1005];
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,m;
    cin>>n>>m;
    memset(g,0,sizeof(g));
    for(int i=0;i<m;i++){
        int x,y;
        cin>>x>>y;
        g[x][y]=1;
        g[y][x]=1;
    }
    for(int u=1;u<=n;u++){
        for(int v=u+1;v<=n;v++){
            if(!g[u][v]){
                e[u].push_back(v);
                e[v].push_back(u);
            }
        }
    }
    memset(c,0,sizeof(c));
    bool ok=1;
    queue<int> q;
    for(int s=1;s<=n&&ok;s++){
        if(c[s])continue;
        q.push(s);
        c[s]=1;
        while(!q.empty()&&ok){
            int x=q.front();
            q.pop();
            int cc=c[x];
            for(int v:e[x]){
                if(!c[v]){
                    c[v]=3-cc;
                    q.push(v);
                }else if(c[v]==cc){
                    ok=0;
                    break;
                }
            }
        }
    }
    cout<<(ok?"DA":"NE")<<endl;
    return 0;
}