AorB study C++ - study code #3

AorB_studyCplusplus_ex3.cpp

#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i = (a); i <= (b); ++i)
#define FORD(i,a,b) for(int i = (a); i >= (b); --i)
#define RI(i,n) FOR(i,1,(n))
#define REP(i,n) FOR(i,0,(n)-1)
#define mini(a,b) a=min(a,b)
#define maxi(a,b) a=max(a,b)
#define mp make_pair
#define pb push_back
#define st first
#define nd second
#define sz(w) (int) w.size()
typedef vector<int> vi;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
const int inf = 1e9 + 5;
const int nax = 1e7 + 5;

string solve(bool * t, int n) {
	string s;
	while(n > 0 && !t[n-1]) --n;
	if(n == 0) return string("0");
	while(n % 4) ++n;
	for(int i = n - 4; i >= 0; i -= 4) {
		int dig = 0;
		REP(j, 4) if(t[i+j]) dig |= (1 << j);
		if(dig <= 9) s += ('0' + dig);
		else s += ('A' + (dig - 10));
	}
	return s;
}

char sl[nax];
bool t[3][nax];
int n[3];

int to_int(char znak) {
	if('0' <= znak && znak <= '9')
		return znak - '0';
	else
		return 10 + (znak - 'A');
}

void te() {
	int k;
	scanf("%d", &k);
	REP(which, 3) {
		scanf("%s", sl);
		int len = strlen(sl);
		n[which] = 0;
		FORD(i, len - 1, 0) {
			int dig = to_int(sl[i]);
			REP(j, 4) t[which][n[which]++] = dig & (1 << j);
		}
		//REP(i, n[which]) printf("%d", (int) t[which][i]); puts("");
	}
	int max_n = max(n[0], max(n[1], n[2]));
	REP(i, max_n) {
		if(t[2][i]) {
			if(!t[0][i] && !t[1][i]) {
				--k;
				t[1][i] = true;
			}
		}
		else {
			if(t[0][i]) {
				t[0][i] = false;
				--k;
			}
			if(t[1][i]) {
				t[1][i] = false;
				--k;
			}
		}
	}
	FORD(i, max_n - 1, 0) if(t[2][i] && k > 0) {
		if(t[0][i]) {
			if(t[1][i]) {
				--k;
				t[0][i] = false;
			}
			else if(k >= 2) {
				k -= 2;
				t[0][i] = false;
				t[1][i] = true;
			}
		}
	}
	if(k < 0) {
		puts("-1");
	}
	else {
		printf("%s\n", solve(t[0], max_n).c_str());
		printf("%s\n", solve(t[1], max_n).c_str());
	}
	REP(j,3) REP(i, max_n + 2) t[j][i] = false;
}
		

int main() {
	int z;
	scanf("%d", &z);
	while(z--) te();
	return 0;
}