Codeforces 474 D. Flowers
Codeforces
2023-09-11 14:14:10 时间
简单递推....
#include <iostream> #include <cstring> #include <cstdio> #include <algorithm> using namespace std; typedef long long int LL; const LL MOD=1000000007; const int maxn=100100; int t,k; LL tui[maxn]; LL sum[maxn]; void TUI(int k) { tui[1]=1; if(1==k) tui[1]++; tui[0]=1; sum[0]=0; sum[1]=tui[1]; for(int i=2;i<maxn;i++) { if(i-k>=0) tui[i]=(tui[i-1]+tui[i-k])%MOD; else tui[i]=tui[i-1]%MOD; } for(int i=2;i<maxn;i++) { sum[i]=(sum[i-1]+tui[i])%MOD; } } int main() { scanf("%d%d",&t,&k); TUI(k); sum[0]=0; while(t--) { int l,r; scanf("%d%d",&l,&r); cout<<(sum[r]-sum[l-1]+MOD*2)%MOD<<endl; } return 0; }
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