// Only GOD
// believe in yourself
// Nemidam Del Be In Darde Donya!
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
typedef long double ld;
typedef pair<int, int> pii;
#define F first
#define S second
#define pb push_back
#define all(x) x.begin(), x.end()
#define bit(x, y) ((x >> y)&1)
#define sz(x) (int)x.size()
#define kill(x) return cout << x << '\n', void()
#define KILL(x) return cout << x << '\n', 0
const int N = 2e3+10;
const int MOD = 1e9+7;
int dp[N][N], inv[N], fac[N];
map<int, int> cnt;
int a[N];
int mul(int a, int b){
a %= MOD, b %= MOD;
return (a*b)%MOD;
}
int C(int n, int k){
if(k > n)
return 0;
return mul(mul(fac[n], inv[n-k]), inv[k]);
}
int pw2(int a, int b){
int res = 1;
while(b){
if(b & 1)
res = mul(res, a);
a = mul(a, a);
b >>= 1;
}
return res;
}
int hasher(string s){
int res = 0;
int pw = 1;
for(int i = 0; i < sz(s); i++){
res += (s[i]-'a'+1)*pw;
pw *= 27;
}
return res;
}
int f(int x){
return (x*(x-1))/2;
}
int32_t main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int n, k;
cin >> n >> k;
fac[0] = 1;
for(int i = 1;i <= n; i++)
fac[i] = mul(fac[i-1], i);
for(int i = 0; i <= n; i++)
inv[i] = pw2(fac[i], MOD-2);
for (int i = 0;i < n; i++){
string s;
cin >> s;
sort(all(s));
cnt[hasher(s)]++;
}
int all = 1;
for(auto u : cnt){
a[all++] = u.S;
}
dp[0][0] = 1;
int ans = 0;
for(int i = 1; i < all; i++){
for(int j=0; j <= k; j++){
for(int t = 0; t <= a[i]; t++){
int X = f(t);
dp[i][j] = (mul(C(a[i], t) , dp[i-1][j-X]) + dp[i][j]) % MOD;
}
}
ans = (ans + dp[i][k])%MOD;
}
cout << ans;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
340 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
596 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
340 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
