Investigating Div-Sum Property UVA - 11361

定问在[A,B] 中，有多少个整数本身能被m整除，各个数位上数字之和也能被m整除？

#include <iostream>
#include <cstring>
#include <vector>
using namespace std;
vector<int> a;
 int m,f[40][105][105][2];
 
 int dfs(int x,int v1,int v2,int flg){
 	if(x<0)
 		return (v1==0&&v2==0);
 	if(f[x][v1][v2][flg]!=-1) return f[x][v1][v2][flg]; 
 	
 	int end= (flg?a[x]:9);
 	int t=0;
 	for(int i=0;i<=end;i++){
 		t+=dfs(x-1,(v1+i)%m,(v2*10+i)%m,flg&&(i==end));
 	}
 	if(flg==0) f[x][v1][v2][flg]=t;
 	return t;
 }
 int sov(int x){
 	a.clear();
 	memset(f,-1,sizeof f);
 	while(x){
 		a.push_back(x%10);
 		x/=10 ;
 	}
 	return dfs(a.size()-1,0,0,1);
 }
 signed main(){
 	int tes; cin>>tes;
 	while(tes--){
 		int x,y;
 		cin>>x>>y>>m;
 		if(m>=100){ cout<<0<<endl;continue;}
 	
 		cout<< sov(y)-sov(x-1) <<endl;
 	}
 }