codeforces#659 div2C传递闭包

题目链接

比赛的时候闭包传递出问题了，赛后找了一些ac代码，发现了问题

AC代码：

/*
 * @Author: hesorchen
 * @Date: 2020-07-03 17:05:01
 * @LastEditTime: 2020-07-25 13:08:03
 * @Description: https://hesorchen.github.io/
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
#define endl '\n'
#define PI acos(-1)
#define PB push_back
#define ll long long
#define INF 0x3f3f3f3f
#define mod 1000000007
#define pll pair
#define lowbit(abcd) (abcd & (-abcd))
#define max(a, b) ((a > b) ? (a) : (b))
#define min(a, b) ((a < b) ? (a) : (b))

#define IOS                      \
    ios::sync_with_stdio(false); \
    cin.tie(0);                  \
    cout.tie(0);
#define FRE                              \
    {                                    \
        freopen("in.txt", "r", stdin);   \
        freopen("out.txt", "w", stdout); \
    }

inline ll read()
{
    ll x = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9')
    {
        if (ch == '-')
            f = -1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9')
    {
        x = (x << 1) + (x << 3) + (ch ^ 48);
        ch = getchar();
    }
    return x * f;
}
//head==============================================================================

string a, b;

int mp[20][20];
int main()
{
    IOS;
    int t;
    cin >> t;
    while (t--)
    {

        fill(mp[0], mp[0] + 20 * 20, 0);
        int n, flag = 1;
        cin >> n >> a >> b;
        for (int i = 0; i < n; i++)
            if (a[i] > b[i])
            {
                flag = 0;
                break;
            }
        if (!flag)
        {
            cout << "-1\n";
            continue;
        }
        for (int i = 0; i < n; i++)
            if (a[i] != b[i])
                mp[a[i] - 'a'][b[i] - 'a'] = 1;
        int ans = 0;
        for (int i = 0; i < 20; i++)
            for (int j = i + 1; j < 20; j++)
                if (mp[i][j])
                {
                    ans++;
                    for (int k = j + 1; k < 20; k++)
                        mp[j][k] |= mp[i][k];
                    break;
                }
        cout << ans << endl;
    }
    return 0;
}

/*


*/