#include <bits/stdc++.h> using namespace std; #define ll long long #define ull unsigned long long #define ld long double #define bigint __int128 #define emb emplace_back #define pb push_back #define pii pair <int, int> #define fi first #define se second #define all(v) v.begin(), v.end() #define Task "" #define MASK(k) (1ull << k) #define bitcnt(k) __builtin_popcount(k) #define testBit(n, k) ((n >> k) & 1) #define flipBit(n, k) (n ^ (1ll << k)) #define offBit(n, k) (n & ~MASK(k)) #define onBit(n, k) (n | (1ll << k)) template <class T> bool minimize(T &a, T b) {if (a > b) {a = b; return true;} return false;} template <class T> bool maximize(T &a, T b) {if (a < b) {a = b; return true;} return false;} const int N = 1e5 + 5, lim = 60, mod = 1e9 + 7; const ll INF = 1e18; struct SegmentTree { // max dist[u] - 2 * dist[p] + dist[v] struct Node { ll A, B, AB, BC, total; Node () { A = B = total = -INF; AB = BC = -INF; } Node (ll x) { A = x; B = -2 * x; AB = BC = -x; total = 0; } void increase(ll val) { A += val; B -= 2 * val; AB -= val; BC -= val; } Node operator + (const Node &other) { Node res; res.A = max(A, other.A); res.B = max(B, other.B); res.AB = max({AB, other.AB, A + other.B}); res.BC = max({BC, other.BC, B + other.A}); res.total = max({total, other.total, A + other.BC, AB + other.A}); return res; } }; vector <Node> st; vector <ll> lazy; SegmentTree (int n) { st.assign(n * 4 + 5, Node(0)); lazy.assign(n * 4 + 5, 0); } void push_down(int id) { ll k = lazy[id]; lazy[id] = 0; st[id << 1].increase(k); lazy[id << 1] += k; st[id << 1 | 1].increase(k); lazy[id << 1 | 1] += k; } void update(int id, int l, int r, int u, int v, ll val) { if (u > r || v < l) return; if (u <= l && r <= v) { st[id].increase(val); lazy[id] += val; return; } int mid = (l + r) >> 1; push_down(id); update(id << 1, l, mid, u, v, val); update(id << 1 | 1, mid + 1, r, u, v, val); st[id] = st[id << 1] + st[id << 1 | 1]; } ll get() { return st[1].total; } }; struct Edge { int u, v; ll w; Edge () {} Edge (int a, int b, ll c) { u = a; v = b; w = c; } } edge[N]; int n, q; ll W, dist[N]; vector <int> adj[N]; int childEdge[N]; int tin[N], tout[N], tour[N << 1], dfsTimes = 0; void dfs(int u, int p = -1) { tin[u] = tout[u] = ++dfsTimes; tour[dfsTimes] = u; for (int i: adj[u]) { int v = edge[i].u ^ edge[i].v ^ u; if (v != p) { childEdge[i] = v; dist[v] = dist[u] + edge[i].w; dfs(v, u); tout[u] = ++dfsTimes; tour[dfsTimes] = u; } } } int main() { ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); if (fopen(Task".inp", "r")) { freopen(Task".inp", "r", stdin); freopen(Task".out", "w", stdout); } cin >> n >> q >> W; for (int i = 0; i < n - 1; i++) { int u, v; ll w; cin >> u >> v >> w; edge[i] = Edge(u, v, w); adj[u].emplace_back(i); adj[v].emplace_back(i); } dfs(1); SegmentTree ST(dfsTimes); for (int i = 1; i <= dfsTimes; i++) { ST.update(1, 1, dfsTimes, i, i, dist[tour[i]]); } ll ans = 0; while (q--) { int d, e; cin >> d >> e; d = (d + ans) % (n - 1); e = (e + ans) % W; int v = childEdge[d]; ST.update(1, 1, dfsTimes, tin[v], tout[v], -edge[d].w + e); edge[d].w = e; ans = ST.get(); cout << ans << '\n'; } }

diameter.cpp: In function 'int main()':
diameter.cpp:121:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |                 freopen(Task".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
diameter.cpp:122:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |                 freopen(Task".out", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~