每个连通块分别取min{白色，黑色}
//#pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<cstdlib> #include<algorithm> #include<iostream> #include<sstream> #include<cmath> #include<climits> #include<string> #include<map> #include<queue> #include<vector> #include<stack> #include<set> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<int,int> pii; #define pb(a) push(a) #define INF 0x1f1f1f1f #define lson idx<<1,l,mid #define rson idx<<1|1,mid+1,r #define PI 3.1415926535898 template<class T> T min(const T& a,const T& b,const T& c) { return min(min(a,b),min(a,c)); } template<class T> T max(const T& a,const T& b,const T& c) { return max(max(a,b),max(a,c)); } void debug() { #ifdef ONLINE_JUDGE #else freopen("d:\in1.txt","r",stdin); freopen("d:\out1.txt","w",stdout); #endif } int getch() { int ch; while((ch=getchar())!=EOF) { if(ch!=' '&&ch!=' ')return ch; } return EOF; } const int maxn=222; vector<int> g[maxn]; int col[maxn]; int num,all,res; bool dfs(int u,int color) { col[u]=color; all++; if(color==1)num++; for(int i=0;i<g[u].size();i++) { int v=g[u][i]; if(!col[v]) {if(!dfs(v,3-color))return false;} else if(col[u]==col[v])return false; } return true; } bool solve(int n) { memset(col,0,sizeof(col)); res=0; for(int i=0;i<n;i++) if(!col[i]) { num=0; all=0; if(!dfs(i,1))return false; int x=min(num,all-num); if(x==0)x++; res+=x; } return true; } int main() { int t; scanf("%d",&t); for(int ca=1;ca<=t;ca++) { int n,m; scanf("%d%d",&n,&m); for(int i=0;i<n;i++) g[i].clear(); for(int i=0;i<m;i++) { int u,v; scanf("%d%d",&u,&v); g[u].push_back(v); g[v].push_back(u); } int flag=solve(n); printf("%d ",flag?res:-1); } return 0; }