CSES - NOI 2019 Open - Results
Submission details
Task:Graph Ordering
Sender:wakaka
Submission time:2019-03-16 08:26:15 +0200
Language:C++
Status:READY
Result:100
Feedback
groupverdictscore
#1ACCEPTED7
#2ACCEPTED29
#3ACCEPTED18
#4ACCEPTED21
#5ACCEPTED25
Test results
testverdicttimegroup
#1ACCEPTED0.40 s1, 4, 5details
#2ACCEPTED0.42 s1, 5details
#3ACCEPTED0.26 s1, 5details
#4ACCEPTED0.34 s1, 5details
#5ACCEPTED0.34 s1, 5details
#6ACCEPTED0.03 s2, 3, 5details
#7ACCEPTED0.03 s2, 3, 5details
#8ACCEPTED0.03 s2, 3, 4, 5details
#9ACCEPTED0.03 s2, 3, 4, 5details
#10ACCEPTED0.03 s2, 3, 4, 5details
#11ACCEPTED0.03 s2, 3, 5details
#12ACCEPTED0.04 s2, 3, 5details
#13ACCEPTED0.04 s2, 3, 4, 5details
#14ACCEPTED0.04 s2, 3, 4, 5details
#15ACCEPTED0.03 s2, 3, 4, 5details
#16ACCEPTED0.03 s2, 3, 4, 5details
#17ACCEPTED0.03 s2, 3, 4, 5details
#18ACCEPTED0.04 s2, 3, 4, 5details
#19ACCEPTED0.04 s3, 4, 5details
#20ACCEPTED0.03 s3, 4, 5details
#21ACCEPTED0.04 s3, 4, 5details
#22ACCEPTED0.04 s3, 4, 5details
#23ACCEPTED0.03 s3, 5details
#24ACCEPTED0.04 s3, 5details
#25ACCEPTED0.03 s3, 5details
#26ACCEPTED0.04 s3, 5details
#27ACCEPTED0.04 s3, 5details
#28ACCEPTED0.67 s5details
#29ACCEPTED0.69 s5details
#30ACCEPTED0.66 s4, 5details
#31ACCEPTED0.63 s4, 5details
#32ACCEPTED0.64 s4, 5details
#33ACCEPTED0.64 s4, 5details
#34ACCEPTED0.67 s5details
#35ACCEPTED0.63 s5details
#36ACCEPTED0.63 s5details
#37ACCEPTED0.04 s1, 2, 3, 4, 5details
#38ACCEPTED0.02 s2, 3, 5details
#39ACCEPTED0.03 s2, 3, 5details
#40ACCEPTED0.03 s2, 3, 5details
#41ACCEPTED0.04 s1, 2, 3, 5details
#42ACCEPTED0.03 s2, 3, 5details
#43ACCEPTED0.03 s3, 4, 5details
#44ACCEPTED0.05 s3, 4, 5details
#45ACCEPTED0.04 s2, 3, 4, 5details
#46ACCEPTED0.02 s2, 3, 4, 5details
#47ACCEPTED0.03 s2, 3, 5details
#48ACCEPTED0.04 s3, 4, 5details
#49ACCEPTED0.05 s4, 5details

Compiler report

input/code.cpp: In function 'int main()':
input/code.cpp:133:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~
input/code.cpp:137:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
   ~~~~~^~~~~~~~~~~~~~~~

Code

#include <bits/stdc++.h>
using namespace std;
#define db(x) cerr << #x << "=" << x << endl
#define db2(x, y) cerr << #x << "=" << x << "," << #y << "=" << y << endl
#define db3(x, y, z) cerr << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z << endl
#define dbv(v) cerr << #v << "="; for (auto _x : v) cerr << _x << ", "; cerr << endl
#define dba(a, n) cerr << #a << "="; for (int _i = 0; _i < (n); ++_i) cerr << a[_i] << ", "; cerr << endl
typedef long long ll;
typedef long double ld;
const int MAXN = 100005;
const int MAXM = 200005;
vector<int> E[MAXN];
pair<int, int> edges[MAXM];
namespace blockcut {
vector<int> preorder;
int low[MAXN]; // topmost vertex a descendent can reach via back-edge
int H[MAXN];
bool cut[MAXN]; // cut[x] -> x is a cut vertex
int parent[MAXN];
vector<int> blocke[MAXN]; // all edges in a block
vector<int> blockv[MAXN]; // all vertices in a block
// a tree-edge is rep by the deeper vertex. a block is rep by highest tree edge.
int vblock[MAXN]; // block of the parent-edge (vblock[1] = 0, vblock[blockId] = blockId)
int eblock[MAXM]; // block of edge
vector<int> adjBlock[MAXN]; // cut nodes adjacent to a block
vector<int> adjCut[MAXN]; // blocks adjacent to a cut node, empty means not cut
void go(int x) {
	preorder.push_back(x);
	low[x] = x;
	int totch = 0;
	for (auto y : E[x]) {
		if (H[y] == -1) {
			H[y] = H[x] + 1;
			parent[y] = x;
			++totch;
			go(y);
			if (H[low[y]] < H[low[x]]) low[x] = low[y];
			if (H[low[y]] >= H[x] && x != 1) cut[x] = true;
		} else if (H[y] < H[x] - 1) {
			// This is a backedge that is not to the parent
			if (H[y] < H[low[x]]) low[x] = y;
		}
	}
	if (x == 1 && totch > 1) cut[x] = true;
}
void getBlocks(int n, int m) {
	memset(H, -1, sizeof(H));
	H[1] = 0;
	go(1);
	for (int x : preorder) {
		if (!parent[x]) continue;
		if (H[low[x]] < H[parent[x]]) vblock[x] = vblock[parent[x]];
		else vblock[x] = x;
	}
	for (int i = 0; i < m; ++i) {
		auto e = edges[i];
		int deeper = H[e.first] > H[e.second] ? e.first : e.second;
		eblock[i] = vblock[deeper];
	}
	for (int i = 0; i < m; ++i) {
		blocke[eblock[i]].push_back(i);
		blockv[eblock[i]].push_back(edges[i].first);
		blockv[eblock[i]].push_back(edges[i].second);
	}
	// If we need the block-cut tree; this takes n log n
	for (int i = 1; i <= n; ++i) {
		sort(blockv[i].begin(), blockv[i].end());
		blockv[i].erase(unique(blockv[i].begin(), blockv[i].end()), blockv[i].end());
		for (int x : blockv[i]) {
			if (cut[x]) {
				adjCut[x].push_back(i);
				adjBlock[i].push_back(x);
			}
		}
	}
}
};
namespace bipolar {
int H[MAXN];
int low[MAXN];
void dfs(int x) {
	low[x] = x;
	for (auto y : E[x]) {
		if (H[y] == -1) {
			H[y] = H[x] + 1;
			dfs(y);
			if (H[low[y]] < H[low[x]]) low[x] = low[y];
		} else if (H[y] < H[x] - 1) {
			// This is a backedge that is not to the parent
			if (H[y] < H[low[x]]) low[x] = y;
		}
	}
}
bool vis[MAXN];
bool isBefore[MAXN];
list<int> ordering;
list<int>::iterator vpos[MAXN];
void dfsOrder(int x, int p = -1) {
	vis[x] = true;
	if (low[x] != x) { // low[x] == x should only occur for vertex s
		if (isBefore[low[x]]) {
			vpos[x] = ordering.insert(vpos[p], x);
		} else {
			vpos[x] = ordering.insert(next(vpos[p]), x);
		}
		// Update isBefore for relation (parent[x], x)
		isBefore[p] = !isBefore[low[x]];
	}
	for (auto y : E[x])
		if (!vis[y]) dfsOrder(y, x);
}
// NOTE: this modifies edges array E!
void getOrdering(int n, int s, int t) {
	if (n == 2) {
		ordering = {1, 2};
		return;
	}
	memset(H, -1, sizeof(H));
	H[s] = 0;
	// Make sure t is first neighbor of s
	E[s].insert(E[s].begin(), t);
	E[t].push_back(s);
	dfs(s);
	isBefore[s] = false;
	vpos[s] = ordering.insert(ordering.end(), s);
	dfsOrder(s);
}
};
using namespace blockcut;
using namespace bipolar;
int main() {
	int n, m;
	scanf("%d%d", &n, &m);
	map<pair<int, int>, int> mp;
	for (int i = 0; i < m; ++i) {
		int a, b;
		scanf("%d%d", &a, &b);
		E[a].push_back(b);
		E[b].push_back(a);
		edges[i] = {a, b};
		mp[{a, b}] = mp[{b, a}] = i;
	}
	getBlocks(n, m);
	int s = -1, t = -1;
	// Every cut node and every block node has <= two neighbors.
	for (int i = 1; i <= n; ++i) {
		if (adjCut[i].size() > 2 || adjBlock[i].size() > 2) {
			printf("IMPOSSIBLE\n");
			return 0;
		}
	}
	// Get two blocks adjacent to only 1 cut node
	for (int i = 1; i <= n; ++i) {
		if (adjBlock[i].size() == 1) {
			assert(blockv[i].size() >= 2);
			int x = cut[blockv[i][0]] ? blockv[i][1] : blockv[i][0];
			if (s == -1) s = x;
			else t = x;
		}
	}
	if (s == -1) {
		s = 1;
		t = 2;
	}
	getOrdering(n, s, t);
	for (int x : ordering) printf("%d ", x);
}

Test details

Test 1

Group: 1, 4, 5

Verdict: ACCEPTED

input
100000 99999
8326 74462
11810 58064
21677 73087
62986 25005
...

correct output
1 44159 25721 84659 90058 9960...

user output
1 44159 25721 84659 90058 9960...

Test 2

Group: 1, 5

Verdict: ACCEPTED

input
100000 99999
28990 31200
86271 56882
61089 18658
52422 57504
...

correct output
68068 86325 91398 75677 51068 ...

user output
68068 86325 91398 75677 51068 ...

Test 3

Group: 1, 5

Verdict: ACCEPTED

input
100000 99999
29378 80094
12282 29378
96138 29378
61870 29378
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 4

Group: 1, 5

Verdict: ACCEPTED

input
100000 99999
97935 71091
9181 31715
73649 47675
45394 25464
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 5

Group: 1, 5

Verdict: ACCEPTED

input
100000 99999
2897 55594
11759 89041
56061 8717
69672 73046
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 6

Group: 2, 3, 5

Verdict: ACCEPTED

input
100 200
55 10
33 57
68 39
29 27
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 7

Group: 2, 3, 5

Verdict: ACCEPTED

input
100 175
71 86
100 88
83 92
25 73
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 8

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
100 200
26 58
49 25
66 20
20 85
...

correct output
1 2 86 60 34 92 23 4 44 89 76 ...

user output
1 29 18 69 14 5 57 19 8 63 21 ...

Test 9

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
100 195
19 28
63 48
1 57
1 20
...

correct output
12 97 18 74 36 10 78 50 61 95 ...

user output
5 71 24 54 96 39 32 100 90 60 ...

Test 10

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
100 193
48 66
15 67
32 14
36 78
...

correct output
1 56 13 32 14 49 75 93 18 6 54...

user output
1 56 13 32 80 14 22 49 75 93 1...

Test 11

Group: 2, 3, 5

Verdict: ACCEPTED

input
100 195
47 68
57 61
45 17
80 61
...

correct output
57 20 83 41 25 33 60 91 59 7 7...

user output
1 50 70 17 51 18 62 44 48 15 5...

Test 12

Group: 2, 3, 5

Verdict: ACCEPTED

input
100 185
43 78
76 99
78 39
83 61
...

correct output
78 43 32 88 26 28 64 81 7 72 2...

user output
23 40 52 59 92 65 74 14 80 70 ...

Test 13

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
99 132
96 16
18 89
98 50
66 26
...

correct output
1 12 45 71 97 22 35 9 60 27 20...

user output
1 12 45 71 97 22 35 9 60 27 20...

Test 14

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
98 144
25 6
30 34
58 25
31 41
...

correct output
32 7 92 1 63 86 87 14 90 17 81...

user output
1 92 7 32 63 86 87 14 90 17 81...

Test 15

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
96 145
19 70
72 92
27 72
17 85
...

correct output
1 50 30 4 10 48 42 5 70 19 29 ...

user output
1 50 30 4 10 48 42 5 70 19 29 ...

Test 16

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
96 158
79 74
41 70
8 5
73 90
...

correct output
7 59 44 27 1 30 49 28 80 52 15...

user output
32 37 96 53 55 76 86 60 93 51 ...

Test 17

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
96 142
95 35
67 89
91 70
48 21
...

correct output
13 20 81 33 1 51 19 69 16 85 6...

user output
1 20 81 33 13 51 19 69 16 85 6...

Test 18

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
72 111
70 17
25 3
58 24
52 9
...

correct output
21 59 48 8 1 2 31 10 11 41 4 5...

user output
1 8 48 59 21 2 31 10 11 41 4 5...

Test 19

Group: 3, 4, 5

Verdict: ACCEPTED

input
988 1563
402 701
830 801
50 578
8 144
...

correct output
1 136 368 683 447 304 131 53 8...

user output
1 136 368 683 447 304 131 53 8...

Test 20

Group: 3, 4, 5

Verdict: ACCEPTED

input
994 1555
171 541
66 915
330 350
494 251
...

correct output
1 164 205 151 951 797 4 654 14...

user output
327 994 678 373 408 519 156 19...

Test 21

Group: 3, 4, 5

Verdict: ACCEPTED

input
1000 2000
711 947
775 441
691 471
844 28
...

correct output
1 676 731 662 248 31 165 558 8...

user output
1 676 731 248 31 662 788 207 6...

Test 22

Group: 3, 4, 5

Verdict: ACCEPTED

input
1000 2000
811 889
873 984
83 52
144 511
...

correct output
60 909 522 568 40 77 181 441 8...

user output
1 46 651 903 478 67 600 60 909...

Test 23

Group: 3, 5

Verdict: ACCEPTED

input
1000 1869
625 715
448 714
110 927
432 1000
...

correct output
224 326 221 30 76 475 666 694 ...

user output
224 326 221 30 76 475 666 694 ...

Test 24

Group: 3, 5

Verdict: ACCEPTED

input
1000 1783
709 1
182 768
355 40
786 260
...

correct output
230 6 135 678 346 19 470 960 3...

user output
6 19 346 678 135 230 470 960 3...

Test 25

Group: 3, 5

Verdict: ACCEPTED

input
1000 2000
92 876
273 598
287 535
526 972
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 26

Group: 3, 5

Verdict: ACCEPTED

input
1000 1910
789 821
553 740
889 527
488 730
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 27

Group: 3, 5

Verdict: ACCEPTED

input
1000 1608
910 416
503 898
928 14
412 903
...

correct output
140 404 739 563 63 794 623 948...

user output
63 794 563 739 404 140 623 948...

Test 28

Group: 5

Verdict: ACCEPTED

input
100000 198666
5659 89691
91040 53375
96642 56177
28768 57001
...

correct output
45598 74078 1039 83702 16344 8...

user output
90 74884 75317 98010 69831 717...

Test 29

Group: 5

Verdict: ACCEPTED

input
100000 197194
41636 91770
63018 23827
39207 93713
67765 47715
...

correct output
79054 61855 53279 55546 60860 ...

user output
1721 7241 18523 86069 96207 52...

Test 30

Group: 4, 5

Verdict: ACCEPTED

input
100000 199985
13674 42886
51349 6858
78502 18751
13628 65936
...

correct output
17857 81664 4369 61462 79754 8...

user output
1 47064 44643 17857 73639 8166...

Test 31

Group: 4, 5

Verdict: ACCEPTED

input
100000 200000
27666 33166
7161 81452
73134 30281
5106 29308
...

correct output
76869 5635 23236 12666 61633 8...

user output
1 73905 50785 14730 66904 9004...

Test 32

Group: 4, 5

Verdict: ACCEPTED

input
100000 200000
62814 54729
98407 26888
91808 70132
58916 49730
...

correct output
19788 11202 3496 24237 68564 5...

user output
1 87874 11202 3496 24237 33785...

Test 33

Group: 4, 5

Verdict: ACCEPTED

input
100000 200000
2299 91653
21125 75544
54029 94067
86513 45051
...

correct output
1 20339 9304 40427 67694 95656...

user output
1 67687 2467 66521 2098 1694 5...

Test 34

Group: 5

Verdict: ACCEPTED

input
100000 200000
34688 93668
78127 18902
55150 33116
273 88797
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 35

Group: 5

Verdict: ACCEPTED

input
100000 200000
21026 14630
5605 59639
25604 78683
55713 70513
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 36

Group: 5

Verdict: ACCEPTED

input
100000 200000
63190 73606
52072 54105
22092 31495
9189 37924
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 37

Group: 1, 2, 3, 4, 5

Verdict: ACCEPTED

input
2 1
2 1

correct output
1 2

user output
1 2 

Test 38

Group: 2, 3, 5

Verdict: ACCEPTED

input
7 9
1 2
1 3
2 3
1 4
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 39

Group: 2, 3, 5

Verdict: ACCEPTED

input
9 12
1 2
2 3
3 1
4 5
...

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 40

Group: 2, 3, 5

Verdict: ACCEPTED

input
5 5
4 2
4 3
2 1
3 1
...

correct output
4 2 3 1 5

user output
2 4 3 1 5 

Test 41

Group: 1, 2, 3, 5

Verdict: ACCEPTED

input
4 3
1 2
3 2
4 2

correct output
IMPOSSIBLE

user output
IMPOSSIBLE

Test 42

Group: 2, 3, 5

Verdict: ACCEPTED

input
17 30
4 1
3 14
6 16
13 6
...

correct output
7 8 11 15 1 2 9 3 14 13 5 10 1...

user output
2 5 9 3 13 14 10 17 12 16 6 4 ...

Test 43

Group: 3, 4, 5

Verdict: ACCEPTED

input
992 1712
377 709
847 640
261 902
761 693
...

correct output
870 1 925 928 950 257 766 520 ...

user output
1 870 925 928 90 552 366 826 6...

Test 44

Group: 3, 4, 5

Verdict: ACCEPTED

input
990 1672
305 445
800 155
365 779
824 247
...

correct output
108 461 160 696 895 655 376 21...

user output
1 326 88 160 461 213 376 655 8...

Test 45

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
99 169
35 32
97 43
22 62
33 7
...

correct output
19 70 62 22 54 78 25 14 3 81 1...

user output
1 19 70 62 22 3 81 17 54 78 25...

Test 46

Group: 2, 3, 4, 5

Verdict: ACCEPTED

input
99 164
62 73
19 35
55 92
79 91
...

correct output
21 25 64 90 17 15 89 95 70 33 ...

user output
1 75 38 96 42 16 33 70 95 89 1...

Test 47

Group: 2, 3, 5

Verdict: ACCEPTED

input
53 68
7 46
51 14
3 18
8 40
...

correct output
32 30 38 33 27 12 8 20 2 34 45...

user output
6 11 35 10 42 21 9 24 49 5 37 ...

Test 48

Group: 3, 4, 5

Verdict: ACCEPTED

input
996 1902
661 201
19 613
895 438
180 32
...

correct output
220 795 198 239 40 164 773 834...

user output
17 490 252 996 693 330 77 288 ...

Test 49

Group: 4, 5

Verdict: ACCEPTED

input
6110 11528
3366 4718
3226 2188
5022 1186
3205 5349
...

correct output
1 2527 2211 554 4201 4522 1494...

user output
433 5664 1304 3522 5541 4274 4...