1 files changed, 21 insertions, 0 deletions
diff --git a/content/datastructures/fenwickTree2.cpp b/content/datastructures/fenwickTree2.cpp
new file mode 100644
index 0000000..9384e3c
--- /dev/null
+++ b/content/datastructures/fenwickTree2.cpp
@@ -0,0 +1,21 @@
+vector<ll> add, mul;
+
+void update(int l, int r, ll val) {
+	for (int tl = l + 1; tl < sz(add); tl += tl & -tl)
+		add[tl] += val, mul[tl] -= val * l;
+	for (int tr = r + 1; tr < sz(add); tr += tr & -tr)
+		add[tr] -= val, mul[tr] += val * r;
+}
+
+void init(vector<ll>& v) {
+	mul.assign(sz(v) + 1, 0);
+	add.assign(sz(v) + 1, 0);
+	for(int i = 0; i < sz(v); i++) update(i, i + 1, v[i]);
+}
+
+ll prefix_sum(int i) {
+	ll res = 0; i++;
+	for (int ti = i; ti > 0; ti -= ti & -ti)
+		res += add[ti] * i + mul[ti];
+	return res;
+}