// headers
#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
// types
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
using dbl = double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pli = pair<ll, int>;
using piipi = pair<pii, int>;
using pipii = pair<int, pii>;
using plpii = pair<ll, pii>;
using ppii = pair<pii, pii>;
// loops
#define forx(i, x, y) for (int i = (x); i <= (y); ++i)
#define forn(i, n) for (int i = 0; i < (n); ++i)
#define for1(i, n) for (int i = 1; i <= (n); ++i)
#define rofx(i, x, y) for (int i = x; i >= y; --i)
#define rofn(i, n) for (int i = n-1; i >= 0; --i)
#define rof1(i, n) for (int i = n; i >= 1; --i)
#define fora(x, v) for (auto x : v)
// define shortcuts
#define all(x) begin(x), end(x)
#define pb push_back
#define eb emplace_back
#define F first
#define S second
#define X first
#define Y second
#define MP make_pair
#define MT make_tuple
// functions
template<class T> inline bool hasbit(T x, int i) { return x&(1<<i); }
template<class T> inline T togbit(T x, int i) { return x|(1<<i); }
template<class T> inline T setbit(T x, int i) { return x|(1<<i); }
template<class T> inline T rembit(T x, int i) { return x&~(1<<i); }
template<class T> inline bool setmax(T &a, const T &b) { return b > a ? a = b, true : false; }
template<class T> inline bool setmin(T &a, const T &b) { return b < a ? a = b, true : false; }
template<class T> int compress(vector<T> &v) { sort(all(v)); v.resize(unique(all(v))-v.begin()); return v.size(); }
// read functions
int read_int() { int x; scanf("%d", &x); return x; }
ll read_ll() { ll x; scanf("%" SCNd64, &x); return x; }
ull read_ull() { ull x; scanf("%" SCNu64, &x); return x; }
dbl read_dbl() { dbl x; scanf("%lf", &x); return x; }
void _R(int &x) { x = read_int(); }
void _R(ll &x) { x = read_ll(); }
void _R(dbl &x) { x = read_dbl(); }
void R() {}
template<class T, class... U> void R(T &head, U &... tail) { _R(head); R(tail...); }
// print functions
template<class T> void _W(const T &x) { cout << x; }
void _W(const int &x) { printf("%d", x); }
void _W(const ll &x) { printf("%" PRId64, x); }
void _W(const ull &x) { printf("%" PRIu64, x); }
void _W(const double &x) { printf("%.16f", x); }
void _W(const char &x) { putchar(x); }
void _W(const char *x) { printf("%s", x); }
template<class T> void _W(const vector<T> &x) { for (auto i = x.begin(); i != x.end(); _W(*i++)) if (i != x.cbegin()) putchar(' '); }
void W() {}
template<class T, class... U> void W(const T &head, const U &... tail) { _W(head); putchar(sizeof...(tail) ? ' ' : '\n'); W(tail...); }
// pseudo-random number generator
template<class T, T x1, T x2, T x3, int y1, int y2, int y3>
struct PRNG {
using S = typename make_signed<T>::type;
T s;
PRNG(T _s = 0) : s(_s) {}
T next() {
T z = (s += x1);
z = (z ^ (z >> y1)) * x2;
z = (z ^ (z >> y2)) * x3;
return z ^ (z >> y3);
}
T next(T n) { return next() % n; }
S next(S l, S r) { return l + next(r - l + 1); }
T operator()() { return next(); }
T operator()(T n) { return next(n); }
S operator()(S l, S r) { return next(l, r); }
static T gen(T s) { return PRNG(s)(); }
template<class U>
void shuffle(U first, U last) {
size_t n = last - first;
for (size_t i = 0; i < n; i++) swap(first[i], first[next(i + 1)]);
}
};
PRNG<uint32_t, 0x9E3779B1, 0x85EBCA6B, 0xC2B2AE35, 16, 13, 16> r32;
PRNG<uint64_t, 0x9E3779B97F4A7C15, 0xBF58476D1CE4E5B9, 0x94D049BB133111EB, 30, 27, 31> r64;
// program
int _main();
int main() {
//ios::sync_with_stdio(false), cin.tie(0);
//time_t begin = clock();
int ret = _main();
//time_t end = clock();
//fprintf(stderr, "Program took %.3f seconds to compute\n", ((double)end-begin)/CLOCKS_PER_SEC);
return ret;
}
/************************************************************
CODE STARTS BELOW THIS POINT
************************************************************/
const int MOD = 1e9+7;
int n, start, finish;
inline ll add(ll a, ll b) { return (a+b)%MOD; }
inline ll mul(ll a, ll b) { return (a*b)%MOD; }
const int MAXN = 2010;
ll dp[MAXN][MAXN];
bool vis[MAXN][MAXN];
int solve(int ix, int comp)
{
if (comp == 0)
return 0;
if (ix == n+1)
return comp == 1 ? 1 : 0;
if (vis[ix][comp])
return dp[ix][comp];
vis[ix][comp] = true;
ll &ans = dp[ix][comp];
ans = 0;
if (ix == start || ix == finish) {
ans = add(solve(ix+1, comp), solve(ix+1, comp+1));
} else {
ans = mul(comp-1, add(solve(ix+1, comp-1), solve(ix+1, comp+1)));
int ends = ix < start ? 2 : ix < finish ? 1 : 0;
ans = add(ans, mul(ends, solve(ix+1, comp+1)));
}
return ans;
}
int _main()
{
R(n, start, finish);
W(solve(2, 1));
return 0;
}
Compilation message
kangaroo.cpp: In function 'll read_ll()':
kangaroo.cpp:49:42: warning: format '%ld' expects argument of type 'long int*', but argument 2 has type 'll* {aka long long int*}' [-Wformat=]
ll read_ll() { ll x; scanf("%" SCNd64, &x); return x; }
~~^
kangaroo.cpp: In function 'ull read_ull()':
kangaroo.cpp:50:45: warning: format '%lu' expects argument of type 'long unsigned int*', but argument 2 has type 'ull* {aka long long unsigned int*}' [-Wformat=]
ull read_ull() { ull x; scanf("%" SCNu64, &x); return x; }
~~^
kangaroo.cpp: In function 'void _W(const ll&)':
kangaroo.cpp:60:44: warning: format '%ld' expects argument of type 'long int', but argument 2 has type 'll {aka long long int}' [-Wformat=]
void _W(const ll &x) { printf("%" PRId64, x); }
~^
kangaroo.cpp: In function 'void _W(const ull&)':
kangaroo.cpp:61:45: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'ull {aka long long unsigned int}' [-Wformat=]
void _W(const ull &x) { printf("%" PRIu64, x); }
~^
kangaroo.cpp: In function 'int read_int()':
kangaroo.cpp:48:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
int read_int() { int x; scanf("%d", &x); return x; }
~~~~~^~~~~~~~~~
kangaroo.cpp: In function 'll read_ll()':
kangaroo.cpp:49:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
ll read_ll() { ll x; scanf("%" SCNd64, &x); return x; }
~~~~~^~~~~~~~~~~~~~~~
kangaroo.cpp: In function 'ull read_ull()':
kangaroo.cpp:50:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
ull read_ull() { ull x; scanf("%" SCNu64, &x); return x; }
~~~~~^~~~~~~~~~~~~~~~
kangaroo.cpp: In function 'dbl read_dbl()':
kangaroo.cpp:51:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
dbl read_dbl() { dbl x; scanf("%lf", &x); return x; }
~~~~~^~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
288 KB |
Output is correct |
| 2 |
Correct |
2 ms |
356 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
288 KB |
Output is correct |
| 2 |
Correct |
2 ms |
356 KB |
Output is correct |
| 3 |
Correct |
2 ms |
536 KB |
Output is correct |
| 4 |
Correct |
2 ms |
536 KB |
Output is correct |
| 5 |
Correct |
3 ms |
668 KB |
Output is correct |
| 6 |
Correct |
3 ms |
668 KB |
Output is correct |
| 7 |
Incorrect |
2 ms |
676 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
288 KB |
Output is correct |
| 2 |
Correct |
2 ms |
356 KB |
Output is correct |
| 3 |
Correct |
2 ms |
536 KB |
Output is correct |
| 4 |
Correct |
2 ms |
536 KB |
Output is correct |
| 5 |
Correct |
3 ms |
668 KB |
Output is correct |
| 6 |
Correct |
3 ms |
668 KB |
Output is correct |
| 7 |
Incorrect |
2 ms |
676 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
288 KB |
Output is correct |
| 2 |
Correct |
2 ms |
356 KB |
Output is correct |
| 3 |
Correct |
2 ms |
536 KB |
Output is correct |
| 4 |
Correct |
2 ms |
536 KB |
Output is correct |
| 5 |
Correct |
3 ms |
668 KB |
Output is correct |
| 6 |
Correct |
3 ms |
668 KB |
Output is correct |
| 7 |
Incorrect |
2 ms |
676 KB |
Output isn't correct |
| 8 |
Halted |
0 ms |
0 KB |
- |
