new file: P4427.cpp

P4427.cpp

@@ -0,0 +1,85 @@
+#include<bits/stdc++.h>
+using namespace std;
+const int mod = 998244353;
+int n, m, k;
+int up;
+vector<int> fri[300005];
+int fa[3000005];
+int cnt[300005];
+int son[300005];
+int dfn[300005];
+int rev[300005];
+int top[300005];
+int dep[300005];
+int nowdfn;
+struct SEG{
+    int num[51][1200005];
+    void init(int now, int nl, int nr) {
+        if(nl == nr) {
+            num[0][now] = 1;
+            for(int i = 1; i <= 50; ++i)
+                num[i][now] = (1ll * num[i - 1][now] * dep[rev[nl]]) % mod;
+            return;
+        }
+        int nmid = (nl + nr) >> 1;
+        init(now * 2, nl, nmid);
+        init(now * 2 + 1, nmid + 1, nr);
+        for(int i = 1; i <= 50; ++i) num[i][now] = (1ll * num[i][now * 2] + num[i][now * 2 + 1]) % mod;
+    }
+    int query(int now, int nl, int nr, int l, int r) {
+        if(nl > r || nr < l) return 0;
+        if(l <= nl && nr <= r) return num[k][now];
+        int nmid = (nl + nr) >> 1;
+        return (1ll * query(now * 2, nl, nmid, l, r) + query(now * 2 + 1, nmid + 1, nr, l, r)) % mod;
+    }
+}seg;
+void dfs1(int now, int from) {
+    cnt[now] = 1;
+    for(int i : fri[now]) {
+        if(i == from) continue;
+        fa[i] = now;
+        dep[i] = dep[now] + 1;
+        dfs1(i, now);
+        cnt[now] += cnt[i];
+        if(cnt[i] > cnt[son[now]]) son[now] = i;
+    }
+}
+void dfs2(int now, int from) {
+    dfn[now] = ++nowdfn;
+    rev[nowdfn] = now;
+    top[now] = from;
+    if(son[now]) dfs2(son[now], from);
+    for(int i : fri[now]) {
+        if(i == fa[now] || i == son[now]) continue;
+        dfs2(i, i);
+    }
+}
+int query(int a, int b) {
+    int ans = 0;
+    while(top[a] != top[b]) {
+        if(dep[top[a]] < dep[top[b]]) swap(a, b);
+        ans = (ans + 1ll * seg.query(1, 1, n, dfn[top[a]], dfn[a])) % mod;
+        a = fa[top[a]];
+    }
+    if(dep[a] < dep[b]) swap(a, b);
+    ans = (ans + 1ll * seg.query(1, 1, n, dfn[b], dfn[a])) % mod;
+    return ans;
+}
+int main() {
+    scanf("%d", &n);
+    for(int i = 1, u, v; i < n; ++i) {
+        scanf("%d%d", &u, &v);
+        fri[u].push_back(v);
+        fri[v].push_back(u);
+    }
+    dfs1(1, 0);
+    dfs2(1, 1);
+    seg.init(1, 1, n);
+    scanf("%d", &m);
+    for(up = 1; up <= m; ++up) {
+        int i, j;
+        scanf("%d%d%d", &i, &j, &k);
+        printf("%d\n", query(i, j));
+    }
+    return 0;
+}