UVA 10160 Servicing Stations（状态压缩+迭代加深）

#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N=36;
int i,n,m,x,y,limit;
LL st[N],Lft[N],Final;
bool dfs(int pos,int d,LL St){
	//printf("%d %d %lld\n",d,pos,st);
    if(St==Final)return 1;
    if(pos>n||d==limit)return 0;
    for(int i=pos;i<=n;i++){
    	if((St|Lft[i])!=Final)break;
    	if(st[i]&St==st[i])continue;
        if(dfs(i+1,d+1,St|st[i]))return 1;
    }return 0;
}
void solve(){
    Final=(1LL<<n)-1;
    for(int i=1;i<=n;i++)st[i]=1LL<<(i-1);
    for(int i=1;i<=m;i++){
        scanf("%d%d",&x,&y);
        st[x]|=1LL<<(y-1);
        st[y]|=1LL<<(x-1);
    }for(Lft[n]=st[n],i=n-1;i;i--)Lft[i]=(st[i]|Lft[i+1]);
    for(limit=1;limit<=n;limit++)if(dfs(1,0,0)){printf("%d\n",limit);break;}
}
int main(){
    while(scanf("%d%d",&n,&m),n+m)solve();
    return 0;
}