Submission #77285

#	Time	Username	Problem	Language	Result	Execution time	Memory
77285		tmwilliamlin168	Pipes (BOI13_pipes)	C++14	100 / 100	116 ms	54500 KiB

pipes

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

//are lls needed?

#define ll long long

const int mxN=1e5;
int n, m, eu[mxN], ev[mxN], d[mxN], qu[mxN-1], qt, nx[mxN];
ll a[mxN], b[mxN];
vector<int> adj[mxN];

void fk() {
	cout << 0;
	exit(0);
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> m;
	if(m>n)
		fk();
	for(int i=0; i<n; ++i)
		cin >> a[i];
	for(int i=0; i<m; ++i) {
		cin >> eu[i] >> ev[i], --eu[i], --ev[i];
		adj[eu[i]].push_back(i);
		adj[ev[i]].push_back(i);
		++d[eu[i]];
		++d[ev[i]];
	}
	for(int i=0; i<n; ++i)
		if(d[i]==1)
			qu[qt++]=i;
	for(int qh=0; qh<n-1; ++qh) {
		if(qh>=qt) {
			if((n^qh)&1^1)
				fk();
			int u=-1, l=-1;
			while(!d[++u]);
			ll s1=0;
			for(int v=u, w, s2=1; v!=u||l==-1; l=nx[v], v=w, s2=-s2) {
//				cout << "h2 " << v << endl;
				for(int e : adj[v]) {
					nx[v]=e;
					w=v^eu[e]^ev[e];
					if(d[w]&&e!=l)
						break;
				}
				s1+=s2*a[v];
//				cout << s1 << " " << nx[v] << endl;
			}
			b[l]=s1;
			for(int v=u, w; nx[v]!=l; v^=eu[nx[v]]^ev[nx[v]])
				b[nx[v]]=s1=2*a[v]-s1;
			a[0]=0;
			break;
		}
		int u=qu[qh];
//		cout << "h1 " << u << endl;
		for(int e : adj[u]) {
			int v=u^eu[e]^ev[e];
			if(!d[v])
				continue;
			b[e]=2*a[u];
			a[v]-=a[u];
			if(--d[v]==1)
				qu[qt++]=v;
			break;
		}
		d[u]=0;
	}
	if(a[qu[n-1]])
		fk();
	for(int i=0; i<m; ++i)
		cout << b[i] << "\n";
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:39:13: warning: suggest parentheses around arithmetic in operand of '^' [-Wparentheses]
    if((n^qh)&1^1)
       ~~~~~~^~
pipes.cpp:56:17: warning: unused variable 'w' [-Wunused-variable]
    for(int v=u, w; nx[v]!=l; v^=eu[nx[v]]^ev[nx[v]])
                 ^
pipes.cpp:44:27: warning: 'w' may be used uninitialized in this function [-Wmaybe-uninitialized]
    for(int v=u, w, s2=1; v!=u||l==-1; l=nx[v], v=w, s2=-s2) {
                          ~^~~

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