边查询，点更新的模板题。
#include<iostream> #include<cstdio> #include<cstring> #include<map> #include<vector> #include<stdlib.h> using namespace std; typedef long long LL; const int maxn = 222222; struct Node { int to;int next; }e[maxn*2]; #define lson l,mid,rt<<1 #define rson mid+1,r,rt<<1|1 int head[maxn]; int son[maxn]; int top[maxn]; int father[maxn]; int deep[maxn]; int len;int z; int size[maxn]; int pos[maxn]; int sum[maxn<<2]; void add(int from, int to) { e[len].to = to; e[len].next = head[from]; head[from] = len++; } int edge[maxn][10]; void init(int x) { son[x] = 0; size[x] = 1; for (int i = head[x]; i != -1; i = e[i].next){ int cc = e[i].to; if (cc == father[x]) continue; deep[cc] = deep[x] + 1; father[cc] = x; init(cc); size[x] += size[cc]; if (size[son[x]] < size[cc]) son[x] = cc; } } void dfs(int x, int tp) { pos[x] = ++z;top[x] = tp; if (son[x]) dfs(son[x], tp); for (int i = head[x]; i != -1; i = e[i].next){ int cc = e[i].to; if (cc == father[x] || cc == son[x]) continue; dfs(cc, cc); } } void up(int rt) { sum[rt] = sum[rt << 1] + sum[rt << 1 | 1]; } void update(int key, int ans, int l, int r, int rt) { if (l == r){ sum[rt] = ans; return; } int mid = (l + r) >> 1; if (key <= mid) update(key, ans, lson); else update(key, ans, rson); up(rt); } int ask(int L, int R, int l, int r, int rt) { if (L <= l&&r <= R) return sum[rt]; int mid = (l + r) >> 1; int ans = 0; if (L <= mid) ans += ask(L, R, lson); if (R > mid) ans += ask(L, R, rson); return ans; } int gao(int x, int y) { int ans = 0; int fx = top[x]; int fy = top[y]; while (fx != fy){ if (deep[fx] < deep[fy]){ swap(fx, fy); swap(x, y); } ans += ask(pos[fx], pos[x], 1, z, 1); x = father[fx]; fx = top[x]; } if (x == y) return ans; if (deep[x]>deep[y]) swap(x, y); ans += ask(pos[x] + 1, pos[y], 1, z, 1); return ans; } int main() { int n,q,s; int a,b,c; while (cin >> n >> q >> s){ memset(sum,0,sizeof(sum)); len = 0;z =0; memset(head,-1,sizeof(head)); deep[s]=1 ; for (int i = 1; i < n ; i++){ scanf("%d%d%d", &edge[i][0], &edge[i][1], &edge[i][2]); add(edge[i][0], edge[i][1]); add(edge[i][1], edge[i][0]); } init(1); dfs(1, 1); for (int i = 1; i < n ; i++){ int a = edge[i][0]; int b = edge[i][1]; int c = edge[i][2]; if (deep[a]>deep[b]) swap(edge[i][0], edge[i][1]); update(pos[edge[i][1]], c, 1, z, 1); } while (q--){ scanf("%d", &a); if (a == 0){ scanf("%d", &b); int t = gao(b, s); cout << t << endl; s = b; } else { scanf("%d%d", &b, &c); edge[b][2] = c; update(pos[edge[b][1]], c, 1, z, 1); } } } return 0; }