Without dp solution to cpcr1c

cpcr1c.cpp

#include<bits/stdc++.h>
using namespace std;
void digits(long long int a, vector<int> &arr){
	while(a){
		arr.push_back(a%10);
		a/=10;
	}
}
int digitsum(int indx,int sum,int tight,vector<int> & arr){
	if(indx==-1)
		return sum;
	long long int ret=0;
	int k=(tight)?arr[indx]:9;
	for(int i=0;i<=k;i++){
		int new_tight=(arr[indx]==i)?tight:0;
		ret+=digitsum(indx-1,sum+i,new_tight,arr);
	}
	return ret;
}
int rangesum(long long int a, long long int b){
	memset(dp,-1,sizeof(dp));
	vector<int> digitA;
	digits(a-1,digitA);
	long long int ans1=digitsum(digitA.size()-1,0,1,digitA);
	vector<int> digitB;
	digits(b,digitB);
	long long int ans2=digitsum(digitB.size()-1,0,1,digitB);
	return (ans2-ans1);
}
int main(){
	long long int a,b;
	while(1){
		cin>>a>>b;
		if(a==-1 && b==-1)
			break;
		cout<<rangesum(a,b)<<endl;
	}
}