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## Discussion of Problem 2018. The Debut Album

accepted
Posted by Mikhail 7 May 2018 23:54
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("avx")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define re return
#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define sqrt(x) sqrt(abs(x))
#define mp make_pair
#define pi (3.14159265358979323846264338327950288419716939937510)
#define fo(i, n) for(int i = 0; i < n; ++i)
#define ro(i, n) for(int i = n - 1; i >= 0; --i)
#define unique(v) v.resize(unique(all(v)) - v.begin())

template <class T> T abs (T x) { re x > 0 ? x : -x; }
template <class T> T sqr (T x) { re x * x; }
template <class T> T gcd (T a, T b) { re a ? gcd (b % a, a) : b; }
template <class T> int sgn (T x) { re x > 0 ? 1 : (x < 0 ? -1 : 0); }

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<string> vs;
typedef double D;
typedef long double ld;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef unsigned long long ull;
typedef tree <int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> _tree;

const int maxn = (int) 5e4 + 10;
const int mod = (int) 1e9 + 7;
int dp[maxn][2];

inline int sum (int a, int b) {
re (a + b) % mod;
}

int main() {
int n, a, b;
cin >> n >> a >> b;
dp[0][0] = dp[0][1] = 1;
fo(i, n) {
for (int j = 1; j <= a && i + j <= n; ++j) dp[i + j][0] = sum (dp[i + j][0], dp[i][1]);
for (int j = 1; j <= b && i + j <= n; ++j) dp[i + j][1] = sum (dp[i + j][1], dp[i][0]);
}
cout << sum (dp[n][0], dp[n][1]) << endl;
re 0;
}
Re: accepted
Posted by Orient 8 May 2018 00:49