Submission #158004

#	Time	Username	Problem	Language	Result	Execution time	Memory
158004		DrSwad	Pipes (BOI13_pipes)	C++14	45.37 / 100	761 ms	66516 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "debug.h"
#endif

typedef long long ll;
typedef pair<int, int> pii;

#define x first
#define y second

const int N = 1e5 + 5;

int n, m;
vector<int> c;
vector<set<int>> adj;
vector<pii> e;
vector<ll> ans;

int adjacentNode(int node, int i) {
	assert(i == 0 || i == 1);
	int adj_edge = (i == 0 ? *adj[node].begin() : *adj[node].rbegin());
	int adj_node = e[adj_edge].x ^ e[adj_edge].y ^ node;
	return adj_node;
}

void dfs(int at, int p, int root, vector<pii> &order) {
	int nxt;

	nxt = adjacentNode(at, 0);
	if (nxt != p) order.push_back({at, *adj[at].begin()});
	else {
		nxt = adjacentNode(at, 1);
		if (nxt != p) order.push_back({at, *adj[at].rbegin()});
	}

	if (nxt != root) dfs(nxt, at, root, order);
}

int main() {
	#ifdef LOCAL
	freopen("in", "r", stdin);
	freopen("out", "w", stdout);
	#endif

	scanf("%d %d", &n, &m);

	c.resize(n);
	for (int i = 0; i < n; i++) scanf("%d", &c[i]);

	adj.resize(n);
	e.resize(m);
	for (int i = 0; i < m; i++) {
		int u, v;
		scanf("%d %d", &u, &v);
		u--, v--;
		adj[u].insert(i);
		adj[v].insert(i);
		e[i] = {u, v};
	}

	ans.resize(m);
	for (int i = 0; i < m; i++) {
		if (adj[e[i].x].size() == 1 || adj[e[i].y].size() == 1) {
			ans[i] = 2LL * (adj[e[i].x].size() == 1 ? c[e[i].x] : c[e[i].y]);
			adj[e[i].x].erase(i);
			adj[e[i].y].erase(i);
			c[e[i].x] -= ans[i] / 2;
			c[e[i].y] -= ans[i] / 2;
		}
	}

	for (int i = 0; i < n; i++) {
		if (adj[i].size() > 2) {
			printf("0\n");
			return 0;
		}
	}

	int first_node;
	for (first_node = 0; first_node < n; first_node++) {
		if (adj[first_node].size() == 2) break;
	}

	if (first_node < n) {
		vector<pii> order;
		dfs(first_node, -1, first_node, order);

		ll sum = 2LL * c[first_node];
		ll diff = 0;
		for (int i = 1; i < order.size(); i++) {
			diff = 2LL * c[order[i].x] - diff;
		}

		ans[order[0].y] = (sum - diff) / 2LL;

		for (int i = 1; i < order.size(); i++) {
			ans[order[i].y] = 2LL * c[order[i].x] - ans[order[i - 1].y];
		}
	}

	for (int i = 0; i < m; i++) printf("%lld\n", ans[i]);

	return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:94:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 1; i < order.size(); i++) {
                   ~~^~~~~~~~~~~~~~
pipes.cpp:100:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 1; i < order.size(); i++) {
                   ~~^~~~~~~~~~~~~~
pipes.cpp:49:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:52:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for (int i = 0; i < n; i++) scanf("%d", &c[i]);
                              ~~~~~^~~~~~~~~~~~~
pipes.cpp:58:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 45.370370370370374 / 70