二分图判定，染色法

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;const int N=100010,M=2*N;
int n,m;
struct edge{int v,ne;}e[M];
int h[N],idx;
int color[N];void add(int a,int b){e[++idx]={b,h[a]};h[a]=idx;
}
bool dfs(int u,int c){color[u]=c;for(int i=h[u];i;i=e[i].ne){int v=e[i].v;if(!color[v]){if(dfs(v,3-c))return 1;}else if(color[v]==c)return 1;//有奇环}return 0;
}
int main(){cin>>n>>m;for(int i=0;i<m;i++){int a,b;cin>>a>>b;add(a,b); add(b,a);}bool flag=0;for(int i=1;i<=n;i++)if(!color[i])if(dfs(i,1)){flag=1;//有奇环break;}if(flag) puts("No");else puts("Yes");return 0;
}