From aa20248672a526b4e0444af1ec5c87682ed11c21 Mon Sep 17 00:00:00 2001
From: Kotecha Udit Hitendra <64374551+kirito-udit@users.noreply.github.com>
Date: Sat, 2 Oct 2021 20:08:24 +0530
Subject: [PATCH] Create Fenwick Tree-Range Sum Queries.cpp

---
 Algorithms/Fenwick Tree-Range Sum Queries.cpp | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 Algorithms/Fenwick Tree-Range Sum Queries.cpp

diff --git a/Algorithms/Fenwick Tree-Range Sum Queries.cpp b/Algorithms/Fenwick Tree-Range Sum Queries.cpp
new file mode 100644
index 0000000..94cb3dc
--- /dev/null
+++ b/Algorithms/Fenwick Tree-Range Sum Queries.cpp	
@@ -0,0 +1,31 @@
+struct FenwickTree {
+    vector<int> bit;  // binary indexed tree
+    int n;
+
+    FenwickTree(int n) {
+        this->n = n;
+        bit.assign(n, 0);
+    }
+
+    FenwickTree(vector<int> a) : FenwickTree(a.size()) {
+        for (size_t i = 0; i < a.size(); i++)
+            add(i, a[i]);
+    }
+
+    int sum(int r) {
+        int ret = 0;
+        for (; r >= 0; r = (r & (r + 1)) - 1)
+            ret += bit[r];
+        return ret;
+    }
+
+    int sum(int l, int r) {
+        return sum(r) - sum(l - 1);
+    }
+
+    void add(int idx, int delta) {
+        for (; idx < n; idx = idx | (idx + 1))
+            bit[idx] += delta;
+    }
+};
+