题解

1、深搜dfs

#include<iostream>
#include<vector>
using namespace std;
int t;
string alpha[8]={"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
void dfs(vector<int> s,vector<char> v,int step=0){
    if(step==t){
        for(int i=0;i<v.size();i++)cout<<v[i];
        cout<<endl;
        return;
    }
    string tmp=alpha[s[step]-2];
    for(int j=0;j<tmp.size();j++){
        v.push_back(tmp[j]);
        dfs(s,v,step+1);
        v.pop_back();
    }
}
int main(){
    cin>>t;
    int k;
    long long s=1;
    vector<int> v;
    vector<char> cl;
    for(int i=0;i<t;i++){
        cin>>k;
        v.push_back(k);
        s*=alpha[k-2].size();
    }
    cout<<s<<endl;
    dfs(v,cl);
    return 0;
}

2、广搜bfs

#include<iostream>
#include<queue>
#include<string>
using namespace std;
int n,s[10];
string alpha[10]={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
queue<string>q;
void bfs(){
    string tmp="";
    for(int i=0;i<alpha[s[0]].size();i++)
        q.push({tmp+alpha[s[0]][i]});
    while(!q.empty()){
        string f=q.front();
        q.pop();
        if(f.size()==n)cout<<f<<endl;
        else{
            for(int i=0;i<alpha[s[f.size()]].size();i++)
                q.push({f+alpha[s[f.size()]][i]});
        }
    }
}
int main(){
    int t=1;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>s[i];
        t*=alpha[s[i]].size();
    }
    cout<<t<<endl;
    bfs();
    return 0;
}