Language: C++

#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

class LowestCommonAncestor
{
private:
    vector<vector<int> > to;
    vector<int> depth;
    void dfs(const vector<vector<int> >& edges, int curr, int prev, int cnt)
    {
        depth[curr] = cnt;
        if(prev != -1){
            to[curr].push_back(prev);
            int j = prev;
            for(unsigned k=0; k<to[j].size(); ++k){
                j = to[j][k];
                to[curr].push_back(j);
            }
        }
        for(unsigned i=0; i<edges[curr].size(); ++i){
            int next = edges[curr][i];
            if(next != prev)
                dfs(edges, next, curr, cnt + 1);
        }
    }
    int climb(int curr, int dist)
    {
        int i = 0;
        while(dist > 0){
            if(dist % 2 == 1)
                curr = to[curr][i];
            dist /= 2;
            ++ i;
        }
        return curr;
    }
public:
    LowestCommonAncestor(const vector<vector<int> >& edges, int root)
    {
        int n = edges.size();
        to.assign(n, vector<int>());
        depth.resize(n);
        dfs(edges, root, -1, 0);
    }
    // 2つのノードの最小共通祖先を取得
    int getAncestor(int a, int b)
    {
        int diff = depth[a] - depth[b];
        if(diff < 0)
            b = climb(b, -diff);
        else
            a = climb(a, diff);
        if(a == b)
            return a;

        for(int i=to[a].size()-1; i>=0; --i){
            if(i < (int)to[a].size() && to[a][i] != to[b][i]){
                a = to[a][i];
                b = to[b][i];
            }
        }
        return to[a][0];
    }
    // ノードの深さを取得
    int getDepth(int a)
    {
        return depth[a];
    }
};

class SegmentTree
{
private:
    typedef long long T1;
    typedef long long T2;

    // データの初期値、以下の条件を満たすこと
    // uniteData(v, INIT_DATA) == v
    static const T1 INIT_DATA = 0;
    // 遅延の初期値、以下の条件を満たすこと
    // updateData(prev, size, INIT_DELAY) == prev
    // updateDelay(x, INIT_DELAY) == x
    static const T2 INIT_DELAY = 0;

    // 長さがsizeの区間における前回の計算結果prevに対して、
    // 区間の各要素にパラメータxを用いた更新処理を適用した後の計算結果を返す
    T1 updateData(T1 prev, int size, T2 x){
        return prev + x * size;
    }
    // パラメータx1,x2による2つの更新処理を順に適用した場合に対して、
    // 同じ結果になるような1つの更新処理のパラメータを返す
    T2 updateDelay(T2 x1, T2 x2){
        return x1 + x2;
    }
    // 2つの区間の計算結果v1,v2に対して、
    // その2つの区間を統合した区間における計算結果を返す
    T1 uniteData(T1 v1, T1 v2){
        return v1 + v2;
    }

    int n;
    vector<T1> data;
    vector<T2> delay;
    vector<int> tmp;
    void updateTree(int a, int b, int k, int l, int r, T2 x){
        if(a <= l && r <= b){
            data[k] = updateData(data[k], tmp[k], x);
            delay[k] = updateDelay(delay[k], x);
        }
        else if(a <= r && l <= b){
            for(int i=0; i<2; ++i){
                data[k*2+1+i] = updateData(data[k*2+1+i], tmp[k*2+1+i], delay[k]);
                delay[k*2+1+i] = updateDelay(delay[k*2+1+i], delay[k]);
            }
            delay[k] = INIT_DELAY;
            updateTree(a, b, k*2+1, l, (l+r)/2, x);
            updateTree(a, b, k*2+2, (l+r+1)/2, r, x);
            data[k] = uniteData(data[k*2+1], data[k*2+2]);
        }
    }
    T1 getValue(int a, int b, int k, int l, int r){
        if(a <= l && r <= b){
            return data[k];
        }
        else if(a <= r && l <= b){
            T1 v1 = getValue(a, b, k*2+1, l, (l+r)/2);
            T1 v2 = getValue(a, b, k*2+2, (l+r+1)/2, r);
            return uniteData(v1, v2);
        }
        else{
            return INIT_DATA;
        }
    }
public:
    SegmentTree(int n0){
        n = 1;
        while(n < n0)
            n *= 2;
        data.assign(2*n-1, INIT_DATA);
        delay.assign(2*n-1, INIT_DELAY);
    }
    SegmentTree(const vector<int>& v) : SegmentTree((int)v.size()){
        tmp.resize(2*n-1);
        for(unsigned i=0; i<v.size(); ++i)
            tmp[n-1+i] = v[i];
        for(int k=n-2; k>=0; --k)
            tmp[k] = tmp[k*2+1] + tmp[k*2+2];
    }
    // 区間[a,b]の要素にパラメータxによる更新処理を適用
    void update(int a, int b, T2 x){
        updateTree(a, b, 0, 0, n-1, x);
    }
    // 区間[a,b]の計算結果を返す
    T1 get(int a, int b){
        updateTree(a, b, 0, 0, n-1, 0);
        return getValue(a, b, 0, 0, n-1);
    }
};

int main()
{
    int n, q;
    cin >> n >> q;

    vector<vector<int> > edges(n);
    for(int i=0; i<n-1; ++i){
        int a, b;
        cin >> a >> b;
        edges[a].push_back(b);
        edges[b].push_back(a);
    }
    LowestCommonAncestor lca(edges, 0);

    vector<int> v;
    vector<int> left(n), right(n);
    stack<tuple<int, int, int> > stk;
    stk.push(make_tuple(0, -1, 0));
    while(!stk.empty()){
        int curr, prev, i;
        tie(curr, prev, i) = stk.top();
        stk.pop();

        if(i == edges[curr].size()){
            right[curr] = v.size();
            v.push_back(-1);
            continue;
        }
        stk.push(make_tuple(curr, prev, i + 1));

        int next = edges[curr][i];
        if(next != prev){
            v.push_back(1);
            left[next] = v.size();
            stk.push(make_tuple(next, curr, 0));
        }
    }
    v.pop_back();
    SegmentTree st(v);

    while(--q >= 0){
        int x, a, b;
        cin >> x >> a >> b;

        if(x == 0){
            int c = lca.getAncestor(a, b);
            long long ans = st.get(left[c], left[a] - 1) +
                            st.get(left[c], left[b] - 1);
            cout << ans << endl;
        }
        else{
            st.update(left[a], right[a] - 1, b);
        }
    }

    return 0;
}

Compiler output:
/usr/bin/ld: /tmp/ccoSSuIZ.o: warning: relocation against `_ZN11SegmentTree9INIT_DATAE' in read-only section `.text._ZN11SegmentTreeC2Ei[_ZN11SegmentTreeC5Ei]'
/usr/bin/ld: /tmp/ccoSSuIZ.o: in function `SegmentTree::SegmentTree(int)':
a.cc:(.text._ZN11SegmentTreeC2Ei[_ZN11SegmentTreeC5Ei]+0x7e): undefined reference to `SegmentTree::INIT_DATA'
/usr/bin/ld: a.cc:(.text._ZN11SegmentTreeC2Ei[_ZN11SegmentTreeC5Ei]+0xa5): undefined reference to `SegmentTree::INIT_DELAY'
/usr/bin/ld: warning: creating DT_TEXTREL in a PIE
collect2: error: ld returned 1 exit status