Submission #391891

#	Time	Username	Problem	Language	Result	Execution time	Memory
391891		Kevin_Zhang_TW	007 (CEOI14_007)	C++17	100 / 100	285 ms	17584 KiB

007

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_N = 200010, inf = 1e9;

int n, m, s, d, A, B;
vector<int> edge[MAX_N];

int diss[MAX_N], disd[MAX_N], disa[MAX_N], disb[MAX_N];

void get_dis(int s, int *dis) {
	fill(dis, dis + n + 1, inf);

	queue<int> q;
	q.emplace(s); dis[s] = 0;
	while (q.size()) {
		int x = q.front(); q.pop();
		for (int u : edge[x])
			if (chmin(dis[u], dis[x] + 1))
				q.emplace(u);
	}
}
bool valid(int rest) {
	auto test = [&](int x) {
		int art = diss[x] + rest;
		int ga = art + disa[x], gb = art + disb[x];

		if (max(disa[x], disb[x]) > 1) return false;

		int da = disd[A], db = disd[B];
//
		if (min(disa[x], disb[x]) == 1) {

			if (art <= min(da, db)) return true;
			//if (art < min(da, db)) return true;
			return false;
		}

		assert(abs(ga-gb)==1);

		if (ga <= da && gb <= db) return true;

		return false;
	};

	for (int i = 1;i <= n;++i)
		if (test(i)) return true;
	return false;

}
	
pair<int,int> get(int s, int *dis) {
	int len = dis[A], fr = len;
	for (int i = 1;i <= n;++i) 
		if (disa[i] == disb[i] && disa[i] + dis[i] == len)
			chmin(fr, disa[i]);
	return make_pair(len, fr);
}

int32_t main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> n >> m >> s >> d >> A >> B;
	for (int a, b, i = 0;i < m;++i) {
		cin >> a >> b;
		DE(a, b);
		edge[a].pb(b), edge[b].pb(a);
	}
	get_dis(s, diss), get_dis(d, disd);
	get_dis(A, disa), get_dis(B, disb);

	int res = -inf;

	int ga = disa[s], gb = disb[s];
	int da = disa[d], db = disb[d];

	if (disa[s] == disb[s]) {
		auto [la, fa] = get(s, diss);
		if (disa[d] == disb[d]) {
			auto [lb, fb] = get(d, disd);
			if (fa <= fb) {
				res = lb - la;
			}
			else {
				res = lb - la - 1;
			}
		}
		else {
			int ga = disa[s], gb = disb[s];
			int da = disa[d], db = disb[d];
			res = min(da, db) - ga;
		}
	}
	else {
		res = min(da - ga, db - gb);
	}

	if (res < 0) res = -1;

	cout << res << '\n';

//	if (!valid(0)) return puts("-1"), 0;
//
//	int l = 0, r = n, mid;
//	while (l < r) {
//		mid = l + r >> 1;
//		if (valid(mid+1))
//			l = mid + 1;
//		else
//			r = mid;
//	}
//	cout << l << '\n';
}

Compilation message (stderr)

007.cpp: In function 'int32_t main()':
007.cpp:14:17: warning: statement has no effect [-Wunused-value]
   14 | #define DE(...) 0
      |                 ^
007.cpp:79:3: note: in expansion of macro 'DE'
   79 |   DE(a, b);
      |   ^~
007.cpp:102:22: warning: unused variable 'gb' [-Wunused-variable]
  102 |    int ga = disa[s], gb = disb[s];
      |                      ^~

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70