Submission #475801

#	Time	Username	Problem	Language	Result	Execution time	Memory
475801		maomao90	Aesthetic (NOI20_aesthetic)	C++17	100 / 100	457 ms	49636 KiB

Aesthetic

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

template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}
#define REP(i, s, e) for (int i = s; i < e; i++)
#define RREP(i, s, e) for (int i = s; i >= e; i--)
typedef long long ll;
typedef long double ld;
#define MP make_pair
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
#define MT make_tuple
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;

#ifdef DEBUG
#define debug(args...) printf(args)
#else
#define debug(args...)
#endif

#define INF 1000000005
#define LINF 1000000000000000005
#define MOD 1000000007
#define MAXN 300005

struct edge {
	int v, w, p;
};

int n, m;
vector<edge> adj[MAXN];
int a[MAXN], b[MAXN], w[MAXN], p[MAXN];

priority_queue<pll, vector<pll>, greater<pll>> pq;
ll d1[MAXN], dn[MAXN];
void dij(int s, ll* d) {
	REP (i, 1, n + 1) {
		d[i] = LINF;
	}
	d[s] = 0;
	pq.push(MP(0, s));
	while (!pq.empty()) {
		auto [ud, u] = pq.top(); pq.pop();
		if (ud != d[u]) continue;
		for (edge e : adj[u]) {
			if (mnto(d[e.v], ud + e.w)) {
				pq.push(MP(d[e.v], e.v));
			}
		}
	}
}

ll x;
bool res;
int dep[MAXN], low[MAXN], ptr;
void dfs(int u, int p) {
	dep[u] = low[u] = ptr++;
	for (edge e : adj[u]) {
		if (e.v == p) continue;
		ll od = min(d1[u] + dn[e.v], d1[e.v] + dn[u]) + e.w;
		if (od > x) continue;
		if (dep[e.v] == -1) {
			dfs(e.v, u);
			if (res) return;
			mnto(low[u], low[e.v]);
			if (low[e.v] > dep[u] && od + e.p > x && 
					dep[n] != -1 && dep[n] >= low[e.v])	{
					res = 1;
					return;
			}
		} else {
			mnto(low[u], dep[e.v]);
		}
	}
}

bool isPos(ll x) {
	ptr = 0;
	::x = x;
	res = 0;
	memset(dep, -1, sizeof dep);
	dfs(1, -1);
	return res;
}

int main() {
	scanf("%d%d", &n, &m);
	REP (i, 0, m) {
		scanf("%d%d%d", &a[i], &b[i], &w[i]);
	}
	int mx = 0;
	RREP (i, m - 1, 0) {
		p[i] = mx;
		mxto(mx, w[i]);
	}
	REP (i, 0, m) {
		adj[a[i]].pb({b[i], w[i], p[i]});
		adj[b[i]].pb({a[i], w[i], p[i]});
	}
	dij(1, d1);
	dij(n, dn);
	ll lo = d1[n], hi = p[0] + d1[n] + 5, mid;
	while (lo < hi) {
		mid = lo + hi >> 1;
		if (isPos(mid)) {
			debug("Hi\n");
			lo = mid + 1;
		} else {
			hi = mid;
		}
	}
	printf("%lld\n", lo);
	return 0;
}

Compilation message (stderr)

Aesthetic.cpp: In function 'int main()':
Aesthetic.cpp:114:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  114 |   mid = lo + hi >> 1;
      |         ~~~^~~~
Aesthetic.cpp:97:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   97 |  scanf("%d%d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~
Aesthetic.cpp:99:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   99 |   scanf("%d%d%d", &a[i], &b[i], &w[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 7 / 7
• Subtask 4: 15 / 15
• Subtask 5: 16 / 16
• Subtask 6: 22 / 22
• Subtask 7: 27 / 27