BZOJ1997
显然相交的两条边不能同时在圆的一侧，\(2-sat\)判一下就好了 但这样边数是\(O(m^2)\)的，无法通过此题 但是\(n\)很小，平面图 边数上界为\(3n - 6\)，所以过大的\(m\)可以判掉
#include #include #include #include #include #include #define Redge(u) for (int k = h[u],to; k; k = ed[k].nxt) #define REP(i,n) for (int i = 1; i <= (n); i++) #define mp(a,b) make_pair(a,b) #define cls(s) memset(s,0,sizeof(s)) #define cp pair #define LL long long int using namespace std; const int maxn = 10005,maxm = 8000005,INF = 1000000000; inline int read(){ int out = 0,flag = 1; char c = getchar(); while (c < 48 || c > 57){if (c == '-') flag = -1; c = getchar();} while (c >= 48 && c <= 57){out = (out << 3) + (out << 1) + c - 48; c = getchar();} return out * flag; } int h[maxn],ne; struct EDGE{int to,nxt;}ed[maxm]; int n,m,N,pos[maxn],a[maxn],b[maxn],vis[maxn]; int dfn[maxn],low[maxn],Scc[maxn],st[maxn],scci,cnt,top; inline void build(int u,int v){ed[++ne] = (EDGE){v,h[u]}; h[u] = ne;} void dfs(int u){ dfn[u] = low[u] = ++cnt; st[++top] = u; Redge(u){ to = ed[k].to; if (!dfn[to]){ dfs(to); low[u] = min(low[u],low[to]); } else if (!Scc[to]) low[u] = min(low[u],dfn[to]); } if (dfn[u] == low[u]){ scci++; do { Scc[st[top]] = scci; }while (st[top--] != u); } } int main(){ int T = read(); while (T--){ n = read(); m = read(); REP(i,m) a[i] = read(),b[i] = read(),vis[i] = false; REP(i,n) pos[read()] = i; if (m > 3 * n - 6) {puts("NO"); continue;} REP(i,m){ a[i] = pos[a[i]]; b[i] = pos[b[i]]; if (a[i] > b[i]) swap(a[i],b[i]); if (a[i] + 1 == b[i]) vis[i] = true; } int tmp = m; m = 0; REP(i,tmp) if (!vis[i]){ m++; a[m] = a[i]; b[m] = b[i]; } N = (m << 1); REP(i,N) h[i] = 0; ne = 0; int x,y,xx,yy; for (int i = 1; i <= m; i++){ x = a[i]; y = b[i]; for (int j = i + 1; j <= m; j++){ xx = a[j]; yy = b[j]; if ((x < xx && xx < y && yy > y) || (x < yy && yy < y && xx < x)){ build(i,j + m); build(j + m,i); } } } cnt = scci = top = 0; REP(i,N) dfn[i] = low[i] = Scc[i] = 0; REP(i,N) if (!dfn[i]) dfs(i); int flag = true; REP(i,m) if (Scc[i] == Scc[i + m]){ flag = false; break; } puts(flag ? "YES" : "NO"); } return 0; }
转载于:https://www.cnblogs.com/Mychael/p/9160752.html
