[Explanations] Luo Gu P1061 Jam counting method

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int small_num;
int big_num;
int number;
int num;
int Jam[30];
inline int is_right()
{
    bool v[30];
    memset(v,true,sizeof(v));
    for(int i=1;i<=number;i++)
    {
        if(!v[Jam[i]]) return false;
        else v[Jam[i]]=false;
        if(Jam[i]<Jam[i-1]) return false;
    }
    return true;
}
int main()
{
    scanf("%d %d %d",&small_num,&big_num,&number);
    for(int i=1;i<=number;i++)
    {
        char c;
        cin>>c;
        Jam[i]=c-'a'+1;
    }
    while(Jam[1]<big_num)
    {
        Jam[number]+=1;
        for(int i=number;i>=1;i--)
        {
            if(Jam[i]>big_num)
            {
                Jam[i-1]+=1;
                Jam[i]=Jam[i-1]-1;
            }
        }
        if(is_right())
        {
            for(int i=1;i<=number;i++)
                cout<<(char)(Jam[i]-1+'a');
            num++;
            cout<<endl;
        }
        if(num==5) return 0;
    }
    return 0; 
}