秒懂带注释题解

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
string si[9] = {"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
vector<string> com;

int n;
int a[101];
void dfs(int p, string s, int a[], int n){
    if (p == n) { // 所有数字处理完毕，将当前字符串加入结果
        com.push_back(s);
        return;
    }
    int num = a[p]; // 当前数字
     if (num < 2 || num > 9){
         return;
     }
    string chars = si[num - 2]; // 获取对应的字母字符串
    for (int i = 0; i < chars.size(); i++) {
        char c = chars[i];
        dfs(p + 1, s + c, a, n);
    }
}
int main(){
    cin >> n;
    for(int i = 0; i < n; i++){
        cin >> a[i];
    }
    dfs(0, "", a, n);
    sort(com.begin(), com.end());
    
    // 输出结果
    cout << com.size() << endl;
    for (int i = 0; i < com.size(); i++) {
        cout << com[i] << endl;
    }
    return 0;
}