【BZOJ1064】[Noi2008]假面舞会【DFS】【分类讨论】

来源：互联网发布：淘宝支付密码怎么修改编辑：程序博客网时间：2024/05/17 02:59

【题目链接】

以为要分层图...没思路，去看题解，膜拜proverbs【proverbs的题解】

/* Footprints In The Blood Soaked Snow */#include <cstdio>#include <algorithm>using namespace std;const int maxn = 100005, maxm = 1000005;int n, m, head[maxn], cnt, ans1, ans2, dis[maxn];bool vis[maxn];struct _edge {int v, w, next;} g[maxm << 1];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline void add(int u, int v, int w) {g[cnt] = (_edge){v, w, head[u]};head[u] = cnt++;}inline int intabs(int x) {return x > 0 ? x : -x;}inline int gcd(int a, int b) {for(; b; b ^= a ^= b ^= a %= b);return a;}inline void dfs(int x) {vis[x] = 1;for(int i = head[x]; ~i; i = g[i].next)if(!vis[g[i].v]) dis[g[i].v] = dis[x] + g[i].w, dfs(g[i].v);else ans1 = gcd(ans1, intabs(dis[x] + g[i].w - dis[g[i].v]));}int mx, mi;inline void tree(int x) {vis[x] = 0;mx = max(mx, dis[x]); mi = min(mi, dis[x]);for(int i = head[x]; ~i; i = g[i].next) if(vis[g[i].v])dis[g[i].v] = dis[x] + g[i].w, tree(g[i].v);}int main() {n = iread(); m = iread();for(int i = 1; i <= n; i++) head[i] = -1; cnt = 0;for(int i = 1; i <= m; i++) {int u = iread(), v = iread();add(u, v, 1); add(v, u, -1);}for(int i = 1; i <= n; i++) if(!vis[i]) dfs(i);if(ans1) for(ans2 = 3; ans2 <= ans1 && ans1 % ans2; ans2++);else {ans2 = 3;for(int i = 1; i <= n; i++) if(vis[i]) {mx = mi = dis[i] = 0;tree(i);ans1 += mx - mi + 1;}}if(ans1 < 3) ans1 = ans2 = -1;printf("%d %d\n", ans1, ans2);return 0;}

0 0