codeforces D.Mashmokh and ACM
2015-02-06 08:22
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题意:给你n和k,然后找出b1, b2, ..., bl(1 ≤ b1 ≤ b2 ≤ ... ≤ bl ≤ n),并且对所有的bi+1%bi==0,问有多少这样的序列?
思路:dp[i][j] 表示长度为i,以j为结尾有多少。dp【i】【j】+=dp【i-1】【s】,j%s==0;
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思路:dp[i][j] 表示长度为i,以j为结尾有多少。dp【i】【j】+=dp【i-1】【s】,j%s==0;
#include <cstdio> #include <cstring> #include <algorithm> using namespace std; const int mod=1000000007; int n,k; int dp[2001][2001]; int main() { scanf("%d%d",&n,&k); memset(dp,0,sizeof(dp)); for(int i=1; i<=n; i++) { dp[1][i]=1; } for(int i=1; i<=k; i++) { for(int j=1; j<=n; j++) { for(int s=j; s<=n; s+=j) { dp[i][s]+=dp[i-1][j]; dp[i][s]%=mod; } } } long long ans=0; for(int i=1; i<=n; i++) { ans+=dp[k][i]; ans%=mod; } printf("%lld\n",ans); return 0; }
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