【DFS】Codeforces Round #402 (Div. 2) B. Weird Rounding

#include<cstdio>
#include<algorithm>
using namespace std;
int n,K,Div=1,a[21],m,ans=100;
bool vis[21];
void calc(int now)
{
int t=0;
bool flag=0;
for(int i=m;i>=1;--i) if(!vis[i])
{
if((!flag) && a[i]==0)
return;
t=t*10+a[i];
flag=1;
}
if(t%Div==0)
ans=min(ans,now);
}
void dfs(int cur,int now)
{
if(cur>m)
{
calc(now);
return;
}
vis[cur]=1;
dfs(cur+1,now+1);
vis[cur]=0;
dfs(cur+1,now);
}
int main()
{
//	freopen("b.in","r",stdin);
scanf("%d%d",&n,&K);
bool flag=0;
while(n)
{
a[++m]=n%10;
if(a[m]==0)
flag=1;
n/=10;
}
if(flag)
ans=m-1;
for(int i=1;i<=K;++i)
Div*=10;
dfs(1,0);
printf("%d\n",ans);
return 0;
}