Submission #121562

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
121562	2019-06-26T19:00:18 Z	Adhyyan1252	Pipes (BOI13_pipes)	C++11	100 / 100	151 ms	20588 KB

pipes

#include<bits/stdc++.h>

using namespace std;

#define int long long

struct edge{
	int u, v;
	int val = LONG_LONG_MAX;
};

vector<edge> e;
vector<vector<int> > g;
vector<int> s;
vector<int> st, cycle;
vector<int> cf;
vector<int> c;
int tym = 1;
bool dfs(int cur, int par){
	s[cur] = tym;
	tym++;
	st.push_back(cur);
	for(int u: g[cur]){
		int next = e[u].u + e[u].v - cur;
		if(s[next] == 0){ //child
			if(dfs(next, cur)) return true;
		}else if(next != par){ //back edge
			while(st.back() != next){
				cycle.push_back(st.back());
				st.pop_back();
			}
			cycle.push_back(st.back());
			st.pop_back();
			return true;
		}
	}
	st.pop_back();
	return false;
}

int find(int cur, int parid){
	int sum = 0;
	for(int eid: g[cur]){
		int next = e[eid].u + e[eid].v - cur;
		if(cf[next]) continue;
		if(eid == parid) continue;
		sum += find(next, eid);
	}
	if(parid == -1) return sum;
	e[parid].val = c[cur] - sum;
	return e[parid].val;
}

signed main(){
	ios::sync_with_stdio(false); cin.tie(0);
	int n, m; cin>>n>>m;
	if(m > n){
		cout<<0<<endl;
		return 0;
	}
	c.resize(n);
	for(int i = 0; i < n; i++){
		cin>>c[i]; 
	}
	g.resize(n);
	e.resize(m);
	for(int i = 0; i < m; i++){
		int u, v; cin>>u>>v; u--, v--;
		g[u].push_back(i);
		g[v].push_back(i);
		e[i].u = u;
		e[i].v = v;
	}
	
	s.resize(n);
	cf.resize(n);
	dfs(0, -1);
	//cout<<"REACHED "<<cycle.size()<<endl;
	for(int u: cycle){
		cf[u] = true;
		//cout<<"C: "<<u<<endl;
	}
	if(cycle.size() == 0){
		//its a tree, just dfs from anywhere
		find(0, -1);
	}else if(cycle.size()%2 == 0){
		cout<<0<<endl;
		return 0;
	}else{
		vector<int> off(n);
		int sum = 0;
		int cnt = 1;
		for(int u: cycle){
			off[u] = find(u, -1);
			//cout<<"OFF "<<u<<" "<<off[u]<<" "<<(c[u]-off[u])*cnt<<" "<<cnt<<endl;
			sum += (c[u] - off[u])*(cnt);
			cnt *= -1;
		}
		sum /= 2;
		//cout<<"SUM "<<sum<<endl;
		int id = -1, prev = sum;
		//sum is the value of edge between u and u+1
		for(int i = 0; i < cycle.size(); i++){
			id = -1;
			int u = cycle[i];
			for(int eid: g[u]){
				int next = e[eid].u + e[eid].v - u;
				if(next == cycle[(i+1)%cycle.size()]){
					//found the egde
					id = eid;
					break;
				}
			}
			assert(id != -1);
			e[id].val = c[u] - off[u] - prev;
			prev = e[id].val;
		}
	}
	for(int i = 0; i < e.size(); i++){
		assert(e[i].val != LONG_LONG_MAX);
		cout<<e[i].val*2<<"\n";
	}
	cout.flush();
}

Compilation message

pipes.cpp: In function 'int main()':
pipes.cpp:103:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 0; i < cycle.size(); i++){
                  ~~^~~~~~~~~~~~~~
pipes.cpp:119:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < e.size(); i++){
                 ~~^~~~~~~~~~

Subtask #1

30.0 / 30.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	2 ms	384 KB	Output is correct
2	Correct	2 ms	384 KB	Output is correct
3	Correct	3 ms	512 KB	Output is correct
4	Correct	129 ms	13048 KB	Output is correct
5	Correct	2 ms	384 KB	Output is correct
6	Correct	2 ms	384 KB	Output is correct
7	Correct	2 ms	388 KB	Output is correct
8	Correct	4 ms	384 KB	Output is correct
9	Correct	2 ms	384 KB	Output is correct
10	Correct	3 ms	512 KB	Output is correct
11	Correct	2 ms	512 KB	Output is correct
12	Correct	3 ms	512 KB	Output is correct
13	Correct	83 ms	10588 KB	Output is correct
14	Correct	106 ms	12408 KB	Output is correct
15	Correct	110 ms	13176 KB	Output is correct
16	Correct	96 ms	11280 KB	Output is correct
17	Correct	115 ms	13148 KB	Output is correct
18	Correct	112 ms	13176 KB	Output is correct
19	Correct	151 ms	16244 KB	Output is correct
20	Correct	2 ms	384 KB	Output is correct
21	Correct	3 ms	512 KB	Output is correct
22	Correct	114 ms	13176 KB	Output is correct
23	Correct	78 ms	10536 KB	Output is correct
24	Correct	114 ms	13216 KB	Output is correct
25	Correct	86 ms	11000 KB	Output is correct

Subtask #2

70.0 / 70.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	2 ms	384 KB	Output is correct
2	Correct	2 ms	640 KB	Output is correct
3	Correct	90 ms	15660 KB	Output is correct
4	Correct	2 ms	384 KB	Output is correct
5	Correct	2 ms	384 KB	Output is correct
6	Correct	2 ms	384 KB	Output is correct
7	Correct	2 ms	384 KB	Output is correct
8	Correct	2 ms	384 KB	Output is correct
9	Correct	2 ms	384 KB	Output is correct
10	Correct	2 ms	384 KB	Output is correct
11	Correct	2 ms	384 KB	Output is correct
12	Correct	2 ms	384 KB	Output is correct
13	Correct	2 ms	384 KB	Output is correct
14	Correct	2 ms	384 KB	Output is correct
15	Correct	2 ms	512 KB	Output is correct
16	Correct	3 ms	512 KB	Output is correct
17	Correct	2 ms	512 KB	Output is correct
18	Correct	2 ms	384 KB	Output is correct
19	Correct	2 ms	384 KB	Output is correct
20	Correct	2 ms	384 KB	Output is correct
21	Correct	2 ms	384 KB	Output is correct
22	Correct	2 ms	512 KB	Output is correct
23	Correct	88 ms	14960 KB	Output is correct
24	Correct	120 ms	17396 KB	Output is correct
25	Correct	90 ms	15720 KB	Output is correct
26	Correct	2 ms	384 KB	Output is correct
27	Correct	2 ms	384 KB	Output is correct
28	Correct	2 ms	384 KB	Output is correct
29	Correct	2 ms	384 KB	Output is correct
30	Correct	138 ms	19768 KB	Output is correct
31	Correct	123 ms	19912 KB	Output is correct
32	Correct	97 ms	14836 KB	Output is correct
33	Correct	91 ms	17032 KB	Output is correct
34	Correct	2 ms	384 KB	Output is correct
35	Correct	2 ms	384 KB	Output is correct
36	Correct	2 ms	384 KB	Output is correct
37	Correct	2 ms	384 KB	Output is correct
38	Correct	119 ms	16752 KB	Output is correct
39	Correct	105 ms	14328 KB	Output is correct
40	Correct	117 ms	17096 KB	Output is correct
41	Correct	105 ms	19824 KB	Output is correct
42	Correct	2 ms	384 KB	Output is correct
43	Correct	2 ms	384 KB	Output is correct
44	Correct	2 ms	384 KB	Output is correct
45	Correct	2 ms	384 KB	Output is correct
46	Correct	149 ms	20588 KB	Output is correct
47	Correct	113 ms	17268 KB	Output is correct
48	Correct	137 ms	19764 KB	Output is correct
49	Correct	73 ms	13192 KB	Output is correct
50	Correct	2 ms	384 KB	Output is correct
51	Correct	2 ms	384 KB	Output is correct
52	Correct	2 ms	384 KB	Output is correct
53	Correct	2 ms	384 KB	Output is correct
54	Correct	138 ms	18536 KB	Output is correct