AorB - HackerRank - C++ code study #1

AorB_studyCplusplus_1.cs

#include <bits/stdc++.h>
using namespace std;

#define rep(i, from, to) for (int i = from; i < (to); ++i)
#define trav(a, x) for (auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
void PR(vi &v) { trav(x, v) cout << x << ' '; cout << endl; }

void unhex(char& c) {
	if (0 <= c && c < 10) c = (char)('0' + c);
	else c = (char)('A' + (c - 10));
}

void rehex(char& c) {
	if ('0' <= c && c <= '9') c = (char)(c - '0');
	else c = (char)(c - 'A' + 10);
}

string trim0(string& s) {
	trav(x, s) unhex(x);
	rep(i,0,sz(s)) {
		if (s[i] != '0') return s.substr(i);
	}
	return "0";
}

bool solve() {
	int K, N;
	string a, b, c;
	cin >> K;
	cin >> a >> b >> c;
	N = max(max(sz(a), sz(b)), sz(c));
	a = string(N-sz(a), '0') + a;
	b = string(N-sz(b), '0') + b;
	c = string(N-sz(c), '0') + c;
	trav(x, a) rehex(x);
	trav(x, b) rehex(x);
	trav(x, c) rehex(x);
	int bits[4] = {8,4,2,1};

	rep(i,0,N) trav(bi, bits) {
		if (!(c[i]&bi)) {
			if (a[i]&bi) {
				a[i] &= ~bi;
				--K;
			}
			if (b[i]&bi) {
				b[i] &= ~bi;
				--K;
			}
		}
		else {
			if (!((a[i]&bi) || (b[i]&bi))) {
				b[i] |= bi;
				--K;
			}
		}
	}

	if (K < 0) return false;

	rep(i,0,N) trav(bi, bits) {
		if (c[i]&bi) {
			if ((a[i]&bi) && (b[i]&bi) && K >= 1) {
				a[i] &= ~bi;
				K--;
			}
			else if ((a[i]&bi) && K >= 2) {
				a[i] &= ~bi;
				b[i] |= bi;
				K -= 2;
			}
		}
	}

	cout << trim0(a) << endl;
	cout << trim0(b) << endl;
	return true;
}

int main() {
	cin.sync_with_stdio(false);
	cin.exceptions(cin.failbit);
	int N;
	cin >> N;
	rep(i,0,N) {
		if (!solve()) cout << -1 << endl;
	}
}