#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using T = tuple<ll, ll, ll>;
#define int long long
#define Base 41
#define sz(a) (int)a.size()
#define FOR(i, a, b) for ( int i = a ; i <= b ; i++ )
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)
#define all(x) x.begin() , x.end()
#define pii pair<int , int>
#define fi first
#define se second
#define Lg(x) 31 - __builtin_clz(x)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int MAX = 2e3 + 5;
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void setupIO(){
#define name "Whisper"
//Phu Trong from Nguyen Tat Thanh High School for gifted student
srand(time(NULL));
cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
cout << fixed << setprecision(10);
}
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
string s;
int numQuery, maxLen;
int inv[MAX], fac[MAX];
int power(int a, int exp){
int res = 1;
for ( ; exp > 0; exp >>= 1, a = (1ll * a * a) % Mod) if(exp & 1){
res = (1ll * res * a) % Mod;
}
return res;
}
void genFac(int n){
inv[0] = fac[0] = 1;
for (int i = 1; i <= n; ++i){
fac[i] = fac[i - 1] *i % Mod;
}
inv[n] = power(fac[n], Mod - 2);
for (int i = n; i >= 1; --i) inv[i - 1] = 1ll * inv[i] * i % Mod;
}
int C(int n, int k){
assert(n >= k);
return 1ll * fac[n] * inv[n - k] % Mod * inv[k] % Mod;
}
int A(int n, int k){
assert(n >= k);
return 1ll * fac[n] * inv[n - k] % Mod;
}
int cnt[26], ans[26][26][MAX];
void add(int &x, int y){
x += y;
if (x >= Mod) x %= Mod;
}
void Whisper(){
cin >> s >> numQuery;
int nLen = sz(s);
genFac(nLen);
for (int i = nLen - 1; i >= 0; --i){
int a = s[i] - 'a';
REP(b, 26) FOR(l, 2, i + 2){
add(ans[a][b][l], C(i, l - 2) * cnt[b] % Mod);
}
cnt[a]++;
}
for (int i = 1; i <= numQuery; ++i){
int maxLen; string t;
cin >> maxLen >> t;
int a = t[0] - 'a', b = t[1] - 'a';
cout << ans[a][b][maxLen] << '\n';
}
}
signed main(){
setupIO();
int Test = 1;
// cin >> Test;
for ( int i = 1 ; i <= Test ; i++ ){
Whisper();
if (i < Test) cout << '\n';
}
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
6 ms |
3164 KB |
Output is correct |
2 |
Correct |
6 ms |
2908 KB |
Output is correct |
3 |
Correct |
4 ms |
2908 KB |
Output is correct |
4 |
Correct |
8 ms |
2952 KB |
Output is correct |
5 |
Correct |
29 ms |
4876 KB |
Output is correct |
6 |
Correct |
37 ms |
4996 KB |
Output is correct |
7 |
Correct |
24 ms |
4988 KB |
Output is correct |
8 |
Correct |
22 ms |
4700 KB |
Output is correct |
9 |
Correct |
820 ms |
15956 KB |
Output is correct |
10 |
Correct |
793 ms |
15816 KB |
Output is correct |