CF414B - Mashmokh and ACM

思路

dp。dp[i][j]表示第i位填j时的方案数

ac代码

#include <bits/stdc++.h>

using namespace std;
using i64 = long long;
const i64 inf = 8e18;
typedef pair<int, int> pii;
const int mod = 1e9 + 7;
const int N = 2e3 + 5;

int dp[N][N];
vector<int> g[N];

void solve() {
    int n, k;
    cin >> n >> k;
    for (int i = 1; i <= k; i++) {
        for (int j = 1; j <= n; j ++) {
            if (i == 1) {
                dp[i][j] = 1;
                continue;
            }

            for (auto k : g[j]) {
                dp[i][j] %= mod;
                dp[i][j] += dp[i - 1][k];
                dp[i][j] %= mod;
            }
        }
    }

    int ans = 0;
    for (int i = 1; i <= n; i++) {
        ans %= mod;
        ans += dp[k][i];
        ans %= mod;
    }

    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cout.tie(0);

    for (int i = 1; i <= 2000; i++) 
        for (int j = 1; j <= 2000; j++)
            if (i % j == 0) g[i].push_back(j);
    

    int t = 1;
    //cin >> t;
    while (t --) solve();

    return 0;
}