思维题，推出公式用等比数列求和做一下。
1 #define IO std::ios::sync_with_stdio(0),cin.tie(0),cout.tie(0)
2 #define bug2(x,y) cout<<#x<<" is "<<x<<" "<<#y<<" is "<<y<<endl
3 #define bug(x) cout<<#x<<" is "<<x<<endl;
4 #include<bits/stdc++.h>
5 #define eb emplace_back
6 typedef long long ll;
7 using namespace std;
8 const ll mod = 1e9+7;
9
10 ll fp(ll x, ll y){
11 ll res = 1;
12 while(y){
13 if(y&1) res = res * x % mod;
14 x = x * x % mod;
15 y >>= 1;
16 }
17 return res;
18 }
19
20 void solve(){
21
22 ll l, r, k, x;
23
24 cin >> l >> r >> k;
25
26 if(k >= 10) cout << 0 << endl;
27 else{
28
29 x = 9 / k + 1;
30
31 ll res = fp(x, r - l);
32
33 ll a1 = fp(x, l);
34
35 res = (a1 * ((res - 1 + mod) % mod) % mod) * fp(x - 1, mod - 2) % mod;
36
37 res = res * (x - 1) % mod;
38
39 cout << res <<endl;
40
41 }
42
43 }
44
45 int main(){
46
47 IO;
48 int T;
49 cin >> T;
50 while(T--) {
51 solve();
52 }
53
54
55 }
标签：Function,cout,res,ll,952,Codeforces,mod,define From： https://www.cnblogs.com/ccsu-kid/p/18251225