平面圖中E ≤ V*2-6..

一個圈上2個點的邊可以是在外或者內, 經典的2sat問題..

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#include<cstdio>#include<cstring>#include<algorithm>#include<stack>using namespace std;#define U(x) U[r[x]]#define V(x) V[r[x]]#define H(x) H[r[x]]const int maxn = 20009;struct edge {int to;edge* next;} E[1000000], *pt, *head[maxn];void AddEdge(int u, int v) {pt->to = v; pt->next = head[u]; head[u] = pt++;}int Low[maxn], Dfn[maxn], Scc[maxn], CK, scc_n;int U[maxn], V[maxn], H[maxn], P[maxn], _P[maxn], r[maxn], n;int N, M, T;stack<int> S;void Init() {pt = E;memset(head, 0, sizeof head);scanf("%d%d", &N, &M);for(int i = 0; i < M; i++)scanf("%d%d", U + i, V + i);for(int i = 0; i < N; i++) {scanf("%d", _P + i);P[_P[i]] = i;}for(int i = 0; i < N; i++)H[_P[i]] = _P[(i + 1) % N];n = scc_n = CK = 0;memset(Dfn, 0, sizeof Dfn);memset(Scc, 0, sizeof Scc);while(!S.empty()) S.pop();}bool chk(int l, int r, int _l, int _r) {if(l > r) swap(l, r);if(_l > _r) swap(_l, _r);return (l < _l && _l < r && r < _r) || (_l < l && l < _r && _r < r);}void Tarjan(int x) {Dfn[x] = Low[x] = ++CK;S.push(x);for(edge* e = head[x]; e; e = e->next) if(!Dfn[e->to]) {Tarjan(e->to);Low[x] = min(Low[x], Low[e->to]);} else if(!Scc[e->to])Low[x] = min(Low[x], Dfn[e->to]);if(Dfn[x] == Low[x]) {int t; scc_n++;do {t = S.top(); S.pop();Scc[t] = scc_n;} while(t != x);}}bool Solve() {if(M > 3 * N - 6) return false;for(int i = 0; i < M; i++)if(V[i] != H[U[i]] && U[i] != H[V[i]]) r[n++] = i;for(int i = 0; i < n; i++)for(int j = 0; j < i; j++)if(chk(P[U(i)], P[V(i)], P[U(j)], P[V(j)])) {AddEdge(i * 2, j * 2 + 1);AddEdge(i * 2 + 1, j * 2);AddEdge(j * 2, i * 2 + 1);AddEdge(j * 2 + 1, i * 2);}for(int i = 0; i < 2 * n; i++) {if(!Dfn[i]) Tarjan(i);}for(int i = 0; i < n; i++)if(Scc[i * 2] == Scc[i * 2 + 1]) return false;return true;}int main() {scanf("%d", &T);while(T--) {Init();puts(Solve() ? "YES" : "NO");}return 0;}

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1997: [Hnoi2010]Planar

Time Limit:?10 Sec??Memory Limit:?64 MB
Submit:?1183??Solved:?458
[Submit][Status][Discuss]

Description

Input

Output

Sample Input

Sample Output

HINT

Source

Day1

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轉載于:https://www.cnblogs.com/JSZX11556/p/5011278.html

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