1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
| #include <bits/stdc++.h>
#define rep(i, x, y) for (int i = x; i <= y; i++)
using namespace std;
const int N = 1e5 + 10;
int T, n, num[30][30];
char a[N], b[N];
int main() {
cin >> T;
while (T--) {
cin >> n;
scanf("%s%s", a + 1, b + 1);
bool ff = 1;
rep(i, 1, n) if (a[i] > b[i]) { ff = 0; break; }
if (!ff) { puts("-1"); continue; }
memset(num, 0, sizeof(num));
rep(i, 1, n) {
if (a[i] != b[i])
num[a[i] - 'a'][b[i] - 'a']++;
}
int ans = 0;
rep(i, 0, 25) {
rep(j, i + 1, 25) {
if (num[i][j]) {
++ans;
num[i][j] = 0;
rep(k, j + 1, 25) {
if (num[i][k]) {
num[j][k] += num[i][k], num[i][k] = 0;
}
}
}
}
}
printf("%d\n", ans);
}
return 0;
}
|