Project Euler #40 Champernowne's constant.cpp

/*
   AUTHOR  : Peeyush Yadav
   Problem : Project Euler #40 Champernowne's constant
*/

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f(a,b,c)                for(int a=b;a<c;a++)
#define s(x)                    scanf("%d",&x);
#define sl(x)                   scanf("%lld",&x);
#define p(x)                    printf("%d\n",x);
#define p2(x,y)                 printf("%d %d\n",x,y);
#define pl(x)                   printf("%lld\n",x);
#define pl2(x,y)                printf("%lld %lld\n",x,y);
#define p1d(a,n)                for(int ix=0;ix<n;ix++) printf("%d ",a[ix]); printf("\n");
#define p2d(a,n,m)              for(int ix=0;ix<n;ix++){ for(int jx=0;jx<m;jx++) printf("%d ",a[ix][jx]); printf("\n");}
void input(){
    #ifdef Megamind
            #define DEBUG
            #define TRACE
            freopen("inp.txt","r",stdin);
            //freopen("out1.txt","w",stdout);
    #endif
}
#ifdef TRACE
    #define trace(x)                       cerr<<__FUNCTION__<<":"<<__LINE__<<": "#x" = "<<x<<endl;
    #define trace2(x,y)                    cerr<<__FUNCTION__<<":"<<__LINE__<<": "#x" = "<<x<<" | "#y" = "<<y<<endl;
    #define trace3(x,y,z)                  cerr<<__FUNCTION__<<":"<<__LINE__<<": "#x" = "<<x<<" | "#y" = "<<y<<" | "#z" = "<<z<<endl;
#else
    #define trace(x)
    #define trace2(x,y)
    #define trace3(x,y,z) 
#endif

inline ll power(ll a, ll b, ll m) {
    ll r = 1;
    while(b) {
        if(b & 1) r = r * a % m;
        a = (a * a)% m;
        b >>= 1;
    }
    return r;
}
inline ll power(ll a, ll b) {
     ll r = 1;
    while(b) {
        if(b & 1) r = r * a ;
        a = a * a;
        b >>= 1;
    }
    return r;
}
 
/*........................................................END OF TEMPLATES.......................................................................*/

ll digit[20],sum[20];


ll find(ll num){
	int d=1;
	while(sum[d]<num) d++;
	
	num-=sum[d-1];
	
	ll  number = power(10,d-1);
	ll counter = (num-1)/d,extract = num%d;
	if (!extract) extract = d;
	number += counter;
	
	while(d != extract){
		number/=10;
		d--;
	}
	
	return number%10;
}

int main(){
	input();
	ll temp = 9,ans;
	sum[1]=9;
	f(i,2,18){
		temp*=10;
		sum[i] = sum[i-1] + i*temp;
	}
	
	int t;
	s(t);
	
	while(t--){
		ans = 1;
		f(i,0,7) {
			sl(temp);	
			ans*=find(temp);
		}
		pl(ans);
	}
	
	#ifdef Megamind
		cout << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC * 1000 << " ms." << endl;
    #endif
}