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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,177 @@ | ||
| #include <algorithm> | ||
| #include <cstdio> | ||
| #include <cstring> | ||
| int read() { | ||
| int res = 0, c; | ||
| do | ||
| c = getchar(); | ||
| while(c < '0' || c > '9'); | ||
| while('0' <= c && c <= '9') { | ||
| res = res * 10 + c - '0'; | ||
| c = getchar(); | ||
| } | ||
| return res; | ||
| } | ||
| const int size = 100050, vsiz = 50, mod = 998244353; | ||
| #define asInt64(x) static_cast<long long>(x) | ||
| struct Edge { | ||
| int to, nxt; | ||
| } E[size * 2]; | ||
| int last[size], cnt = 0; | ||
| void addEdge(int u, int v) { | ||
| ++cnt; | ||
| E[cnt].to = v, E[cnt].nxt = last[u]; | ||
| last[u] = cnt; | ||
| } | ||
| bool flag[size], vis[size]; | ||
| struct Info { | ||
| int u, v; | ||
| } VE[vsiz]; | ||
| int ecnt = 0; | ||
| bool DFS(int u, int p) { | ||
| vis[u] = true; | ||
| int siz = 0; | ||
| for(int i = last[u]; i; i = E[i].nxt) { | ||
| int v = E[i].to; | ||
| if(v != p) { | ||
| if(vis[v]) { | ||
| flag[u] = true; | ||
| if(u < v) { | ||
| VE[ecnt].u = u, VE[ecnt].v = v; | ||
| ++ecnt; | ||
| } | ||
| } else | ||
| siz += DFS(v, u); | ||
| } | ||
| } | ||
| if(siz >= 2) | ||
| flag[u] = true; | ||
| return siz | flag[u]; | ||
| } | ||
| int add(int a, int b) { | ||
| a += b; | ||
| return a < mod ? a : a - mod; | ||
| } | ||
| struct Vec { | ||
| int x, y; | ||
| Vec() {} | ||
| Vec(int x, int y) : x(x), y(y) {} | ||
| Vec operator+(const Vec& rhs) const { | ||
| return Vec(add(x, rhs.x), add(y, rhs.y)); | ||
| } | ||
| void operator*=(long long k) { | ||
| x = x * k % mod, y = y * k % mod; | ||
| } | ||
| void operator*=(const Vec& rhs) { | ||
| x = x * asInt64(rhs.x) % mod, | ||
| y = y * asInt64(rhs.y) % mod; | ||
| } | ||
| } k[size][2]; | ||
| long long dot(const Vec& a, const Vec& b) { | ||
| return (asInt64(a.x) * b.x + asInt64(a.y) * b.y) % | ||
| mod; | ||
| } | ||
| struct VT { | ||
| struct Edge { | ||
| int to, nxt; | ||
| Vec a, b; | ||
| } E[vsiz]; | ||
| int last[size], cnt; | ||
| VT() : cnt(0) {} | ||
| void addEdge(int u, int v, const Vec& a, | ||
| const Vec& b) { | ||
| ++cnt; | ||
| E[cnt].to = v, E[cnt].nxt = last[u], | ||
| E[cnt].a = a, E[cnt].b = b; | ||
| last[u] = cnt; | ||
| } | ||
| } vt; | ||
| int dp[size][2]; | ||
| int build(int u) { | ||
| vis[u] = true; | ||
| int link = 0; | ||
| dp[u][0] = dp[u][1] = 1; | ||
| for(int i = last[u]; i; i = E[i].nxt) { | ||
| int v = E[i].to; | ||
| if(!vis[v]) { | ||
| int lv = build(v); | ||
| if(lv) { | ||
| if(flag[u]) | ||
| vt.addEdge(u, lv, | ||
| k[v][0] + k[v][1], | ||
| k[v][0]); | ||
| else | ||
| k[u][0] = k[v][0] + k[v][1], | ||
| k[u][1] = k[v][0], link = lv; | ||
| } else { | ||
| dp[u][0] = dp[u][0] * | ||
| asInt64(dp[v][0] + dp[v][1]) % mod; | ||
| dp[u][1] = | ||
| dp[u][1] * asInt64(dp[v][0]) % mod; | ||
| } | ||
| } | ||
| } | ||
| if(flag[u]) | ||
| k[u][0] = Vec(1, 0), k[u][1] = Vec(0, 1), | ||
| link = u; | ||
| else | ||
| k[u][0] *= dp[u][0], k[u][1] *= dp[u][1]; | ||
| return link; | ||
| } | ||
| int d[size]; | ||
| void preDepth(int u) { | ||
| for(int i = vt.last[u]; i; i = vt.E[i].nxt) { | ||
| int v = vt.E[i].to; | ||
| d[v] = d[u] + 1; | ||
| preDepth(v); | ||
| } | ||
| } | ||
| bool cho[size][2]; | ||
| Vec solve(int u) { | ||
| Vec res(cho[u][1] ? 0 : dp[u][0], | ||
| cho[u][0] ? 0 : dp[u][1]); | ||
| for(int i = vt.last[u]; i; i = vt.E[i].nxt) { | ||
| int v = vt.E[i].to; | ||
| Vec dpv = solve(v); | ||
| res *= Vec(dot(dpv, vt.E[i].a), | ||
| dot(dpv, vt.E[i].b)); | ||
| } | ||
| return res; | ||
| } | ||
| int main() { | ||
| int n = read(); | ||
| int m = read(); | ||
| while(m--) { | ||
| int u = read(); | ||
| int v = read(); | ||
| addEdge(u, v); | ||
| addEdge(v, u); | ||
| } | ||
| DFS(1, 0); | ||
| memset(vis + 1, 0, sizeof(bool) * n); | ||
| flag[1] = true; | ||
| build(1); | ||
| preDepth(1); | ||
| for(int i = 0; i < ecnt; ++i) | ||
| if(d[VE[i].u] > d[VE[i].v]) | ||
| std::swap(VE[i].u, VE[i].v); | ||
| int end = 1 << ecnt, ans = 0; | ||
| for(int i = 0; i < end; ++i) { | ||
| for(int j = 0; j < ecnt; ++j) | ||
| if(i & (1 << j)) | ||
| cho[VE[j].u][1] = cho[VE[j].v][0] = | ||
| true; | ||
| else | ||
| cho[VE[j].u][0] = true; | ||
| Vec res = solve(1); | ||
| ans = add(ans, add(res.x, res.y)); | ||
| for(int j = 0; j < ecnt; ++j) | ||
| if(i & (1 << j)) | ||
| cho[VE[j].u][1] = cho[VE[j].v][0] = | ||
| false; | ||
| else | ||
| cho[VE[j].u][0] = false; | ||
| } | ||
| printf("%d\n", ans); | ||
| return 0; | ||
| } |
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