题解(压缩)

#include<bits/stdc++.h>
using namespace std;string s[10]={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};int num[10]={0,0,3,3,3,3,3,4,3,4};int n,a[15],ans=1;vector<char> v;void dfs(int t){ if(t>n){ for(int i=0;i<n;i++) cout<<v[i]; cout<<endl; return; } for(int i=0;i<s[a[t]].size();i++){ v.push_back(s[a[t]][i]); dfs(t+1); v.pop_back(); }}int main(){ cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; ans*=num[a[i]]; } cout<<ans<<endl; dfs(1); return 0;}