【BZOJ1064】[Noi2008]假面舞会【DFS】【分类讨论】
2016-03-28 17:52
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【题目链接】
以为要分层图...没思路,去看题解,膜拜proverbs【proverbs的题解】
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; }
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