Codeforces 第 976 轮（第 2 单元）（A、B、C、D、E）并发检查集、区间合并、概率 dp-C 问题

思路

所以可以从高位到低位贪心地确定$a$的该位取什么值，然后分类讨论即可。

代码

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5 + 5;
int b, c, d;
void solve()
{
	cin >> b >> c >> d;
	int ans = 0;
	bool ok = true;
	for (int j = 61; j >= 0; j--)
	{
		int bitb = (b >> j) & 1;
		int bitc = (c >> j) & 1;
		int bitd = (d >> j) & 1;
		if (bitd == 1)
		{
			if (bitb == 1 && bitc == 1)continue;
			if (bitb == 1 && bitc == 0)continue;
			if (bitb == 0 && bitc == 1) {ok = false; continue;}
			if (bitb == 0 && bitc == 0)ans += (1ll << j);
		}
		else
		{
			if (bitb == 1 && bitc == 1) {ans += (1ll << j); continue;}
			if (bitb == 1 && bitc == 0) {ok = false; continue;}
			if (bitb == 0 && bitc == 1) {ans += (1ll << j); continue;}
			if (bitb == 0 && bitc == 0)continue;
		}
	}
	if (!ok)
	{
		cout << -1 << endl;
	}
	else
	{
		cout << ans << endl;
	}
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	int test = 1;
	cin >> test;
	for (int i = 1; i <= test; i++)
	{
		solve();
	}
	return 0;
}