Gym - 101246C dfs

char tu[mxn][mxn];
int mp[mxn];
int n,m;
int dp[1<<26];
int lowbit(int x){return x&(-x);}
int init(int state){
if(dp[state])return dp[state];
int ret=0;
while(state){
ret++;
state-=lowbit(state);
}
return dp[state]=ret;
}
int ans;
void dfs(int cur,int k,int state){
if(cur==n+1){
ans=min(ans,max(k,init(state)));return;
}
if(mp[cur])dfs(cur+1,k+1,state);
dfs(cur+1,k,state|mp[cur]);
}
int main(){
//freopen("in.txt","r",stdin);
sf("%d%d",&n,&m);
rep(i,1,n){ sf("%s",tu[i]+1); }
for(int i=1;i<=n;++i){
for(int j=1;j<=m;++j){
if(tu[i][j]=='*')
mp[i]+=(1<<(j-1));
}
}
ans=min(n,m);
dfs(1,0,0);
pf("%d\n",ans);
}