牛牛与数组（牛客、DP）

最新推荐文章于 2024-11-16 12:43:59 发布

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牛牛与数组

#include <iostream>
#include <cstring>
#include <string>
#include <cstdlib>
#include <cstdio>
#include <map>
#include <queue>
#include <vector>
#include <algorithm>
using namespace std;
#define mod 1000000007
typedef long long ll;
const int maxn = 110;

ll dp[20][100100];

int main()
{
    ll n, k;
    scanf("%lld %lld", &n, &k);
    for (ll i = 1; i <= k;i++)
        dp[1][i] = 1;
    for (int i = 2; i <= n;i++)
    {
        ll sum = 0;
        for (int j = 1; j <= k;j++)
            sum += dp[i - 1][j], sum %= mod;
        for (int j = 1; j <= k; j++)
        {
            ll s = 0;
            for (int u = j * 2; u <= k; u += j)
            {
                s += dp[i - 1][u];
                s %= mod;
            }
            dp[i][j] = (sum - s) % mod;
        }
    }
    ll ans = 0;
    for (int i = 1; i <= k;i++)
        ans += dp[n][i], ans %= mod;
    printf("%lld\n", ans);
}