Password UVA - 1262(组合数)

题目链接：点击打开链接

题目思路：先找出每一列相同的个数，然后根据排列组合原理去逐渐确定范围。

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<cmath>
#include<sstream>
#define LL long long
#define INF 0x3f3f3f3f
using namespace std;
const int maxn = 1e5;
int cnt[10];
char mp1[10][10];
char s[10][10];
char mp2[10][10];
int k;
int T;
int vis[26];
char ans[10];
int ok = 0;
void dfs(int now,int sum)
{
    if(now>=5){
        ok = 1;
        return ;
    }
    int tmp = 1;
    for(int i = now+1;i<5;i++){
        tmp *= cnt[i];
    }
    int cntt = tmp;
    for(int i = 0;i<cnt[now];i++){
        if(tmp>=sum){
            ans[now] = s[now][i];
            dfs(now+1,sum);
            break;
        }
        else{
                sum-=tmp;
        }
    }
}
int main()
{
    cout<<pow(16,16)<<endl;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&k);
        for(int i = 0;i<6;i++){
            scanf("%s",mp1[i]);
        }
        for(int i = 0;i<6;i++){
            scanf("%s",mp2[i]);
        }
        for(int j =0;j<5;j++){
            memset(vis,0,sizeof(vis));
            int cntt = 0;
            for(int i = 0;i<6;i++){
                char tmp1 = mp1[i][j];
                    for(int ii = 0;ii<6;ii++){
                        if(tmp1 == mp2[ii][j]&&vis[(int)(tmp1-'A')]==0){
                            s[j][cntt++] = tmp1;
                            vis[tmp1-'A'] = 1;
                        }
                    }
            }
           // cout<<cntt<<endl;
            cnt[j] = cntt;
        }
        int falg = 1;
        int tmp = 1;
        for(int i = 0;i<5;i++){
            tmp*=cnt[i];
            if(cnt[i]==0){
                falg = 0;
            }
        }
        if(!falg||k>tmp){
           // cout<<"fuck"<<endl;
            puts("NO");
        }
        else{
            for(int i = 0;i<6;i++){
                sort(s[i],s[i]+cnt[i]);
            }
            ok = 0;
            dfs(0,k);
            if(!ok)
                puts("NO");
            else{
            cout<<ans<<endl;
            }
        }
    }
}