diff --git a/c++/heavy_light.cpp b/c++/heavy_light.cpp
new file mode 100644
index 0000000..9f5e2c7
--- /dev/null
+++ b/c++/heavy_light.cpp
@@ -0,0 +1,163 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+using namespace __gnu_pbds;
+template <typename T> using ordered_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;
+// orderded_set ->  find_by_order(x)<itr, x being 0-indexed>; order_of_key(x)<count, strictly less>
+
+typedef long long       ll;
+typedef long double     lld;
+typedef pair<int, int>  pii;
+typedef pair<ll, ll>    pll;
+#define loop(n)         for(ll i = 0; i < (n); ++i)
+#define rep(i,zz,n)     for(ll i = zz; i < (n); ++i)
+#define repi(i,zz,n)    for(ll i = zz; i >= (n); --i)
+#define all(v)          v.begin(),v.end()
+#define pb              push_back
+#define ff              first
+#define ss              second
+#define sz(x)           (int)x.size()
+#define nline           cout << '\n'
+
+#define     debug(x)    cout << #x << " "; _print(x); cout << '\n';
+#define     _debug(a,b) cout << #a << " [ "; array_debug(a,b); cout << "]\n";
+template <class T, class V> void array_debug(T *a, V n){ rep(i,0,n) cout << a[i] << ' ';}
+template <class T>          void _print(T t) {cout << t;}
+template <class T, class V> void _print(pair <T, V> p) {cout << "{"; _print(p.ff); cout << ","; _print(p.ss); cout << "}";}
+template <class T>          void _print(vector <T> v) {cout << "[ "; for (T i : v) {_print(i); cout << " ";} cout << "]";}
+template <class T>          void _print(set <T> v) {cout << "[ "; for (T i : v) {_print(i); cout << " ";} cout << "]";}
+template <class T>          void _print(multiset <T> v) {cout << "[ "; for (T i : v) {_print(i); cout << " ";} cout << "]";}
+template <class T, class V> void _print(map <T, V> v) {cout << "[ "; for (auto i : v) {_print(i); cout << " ";} cout << "]";}
+
+const lld eps = 1e-9;
+const int mod = 1e9 + 7;
+const ll inf = 1e18;
+const int N1 = 2e5 + 10;
+
+// vector<vector<int>> adj;
+// vector<ll> val;
+// the vector to work on ..... lets call that "val"
+
+// need to call segtree as well ???
+template<typename T>
+struct HeavyLight {
+    vector<vector<int>> up;
+    vector<int> depth, tin, tout, pos, heavy_child, chain_head;
+    vector<T> tmp;
+    int tmm, n, n1;
+    // SegmentTree<Node> seg;
+
+    void assign() {
+        n = sz(adj), n1 = __lg(n) + 1, tmm = 0;
+        up = vector<vector<int>>(n, vector<int>(n1, -1));
+        depth = vector<int>(n, -1);
+        tin = vector<int>(n);
+        tout = vector<int>(n);
+        pos = vector<int>(n);
+        heavy_child = vector<int>(n, -1);
+        chain_head = vector<int>(n);
+        tmp = vector<T>(n);
+
+        dfs_init(0);
+        rep(i, 1, n1) {
+            rep(j, 0, n) {
+                if (up[j][i - 1] != -1) {
+                    up[j][i] = up[up[j][i - 1]][i - 1];
+                }
+            }
+        }
+
+        tmm = 0;
+        decompose(0, 0);
+        seg.assign(tmp);
+    }
+
+    int dfs_init(int i) {
+        int sz = 1, mxx_chldsz = 0;
+        tin[i] = tmm++;
+        for (int x : adj[i]) {
+            if (x == up[i][0])   continue;
+
+            up[x][0] = i, depth[x] = depth[i] + 1;
+            int cur_sz = dfs_init(x);
+            if (cur_sz > mxx_chldsz)    mxx_chldsz = cur_sz, heavy_child[i] = x;
+            sz += cur_sz;
+        }
+        tout[i] = tmm++;
+        return sz;
+    }
+
+    void decompose(int i, int cur_head) {
+        chain_head[i] = cur_head, pos[i] = tmm++;
+        tmp[pos[i]] = val[i];
+
+        if (heavy_child[i] != -1) decompose(heavy_child[i], cur_head);
+        for (int x : adj[i]) {
+            if (x == up[i][0] || x == heavy_child[i])    continue;
+            decompose(x, x);
+        }
+    }
+
+    bool is_anc(int i, int j) {
+        return tin[i] <= tin[j] && tout[i] >= tout[j];
+    }
+
+    int lca(int x, int y) {
+        if (depth[x] > depth[y])    swap(x, y);
+        if (is_anc(x, y))   return x;
+
+        repi(i, n1 - 1, 0) {
+            if (up[x][i] != -1 && is_anc(up[x][i], y) == 0) {
+                x = up[x][i];
+            }
+        }
+        return up[x][0];
+    }
+
+    // including lca, [lca, i]
+    T query_chain(int i, int lc) {
+        T z = 0;
+        while (chain_head[i] != chain_head[lc]) {
+            z = z + seg.query(1, 0, n - 1, pos[chain_head[i]], pos[i]).sum; //  check !!!!
+            i = up[chain_head[i]][0];
+        }
+        z = z + seg.query(1, 0, n - 1, pos[lc], pos[i]).sum;     //  check !!!!
+        return z;
+    }
+
+    T query(int x, int y) {
+        int lc = lca(x, y);
+        return query_chain(x, lc) + query_chain(y, lc) - val[lc];     //  check !!!!
+        // lc has been included TWICE !!!
+    }
+
+    void update(int i, T x) {
+        val[i] = x;
+        seg.update_one(1, 0, n - 1, pos[i], x);
+        // whether adding or changing should be checked in segtree
+    }
+};
+HeavyLight<ll> hld;   //  check int or ll !!!!
+
+int code() {
+
+    // enter main code
+
+    return 0;
+}
+
+int main() {
+    ios::sync_with_stdio(0); cin.tie(0);
+    // freopen("input.txt","r",stdin);
+    // freopen("output.txt","w",stdout);
+
+    int tc = 1;
+    cin >> tc;
+
+    loop(tc)  code();
+    // rep(i, 1, tc + 1)  cout << "Case #" << i << ": ", code();
+
+    return 0;
+}
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