The process is made of violence enumeration

 # include & lt; Bits/stdc++. H> 

using namespace std; 

Vector a; 
int n; 
Int b [10]. 
Int ret. 
Void DFS (int I) {
If (I==a.s considering ()) {
Ret++; 
} else {
For (int j=0; J & lt; A [I]. The size (); J++) {
If (b [a [I] [j] - '0']) {
B [a [I] [j] - '0')=0. 
DFS (I + 1); 
B [a [I] [j] - '0']=1; 
} 
} 
} 
} 
Int main () {
Cin & gt;> n; 
for(int i=0; i String x; Cin & gt;> x; 
Amy polumbo ush_back (x); 
} 
for(int i=0; i <10; [I] i++) b=1; 
Ret=0; 
DFS (0); 
cout return 0; 
} 

The building Lord stupid, drew a sketch for half a day is not very understand the thinking of it, or have other ideas welcome pointed out