diff --git a/C++/Leetcode/range-sum-query-mutable.cpp b/C++/Leetcode/range-sum-query-mutable.cpp
new file mode 100644
index 0000000..cfc41d8
--- /dev/null
+++ b/C++/Leetcode/range-sum-query-mutable.cpp
@@ -0,0 +1,46 @@
+class NumArray {
+public:
+    vector<int>tree;
+    int n;
+    NumArray(vector<int>& nums) {
+        n=nums.size();
+        tree.assign(2*n,0);
+        for(int i=n;i<2*n;i++)
+            tree[i]=nums[i-n];
+        for(int i=n-1;i>0;i--)
+            tree[i]=tree[i*2]+tree[i*2+1];
+    }
+    
+    void update(int index, int val) {
+        index+=n;
+        tree[index]=val;
+        while(index){
+            int l=index,r=index;
+            if(index%2==0)
+                r=index+1;
+            else
+                l=index-1;
+        tree[index/2]=tree[l]+tree[r];
+        index/=2;
+        }
+        
+    }
+    
+    int sumRange(int l, int r) {
+        l+=n,r+=n;
+        int sum=0;
+        while (l <= r) {
+        if ((l % 2) == 1) {
+           sum += tree[l];
+           l++;
+        }
+        if ((r % 2) == 0) {
+           sum += tree[r];
+           r--;
+        }
+        l /= 2;
+        r /= 2;
+    }
+    return sum;
+    }
+};
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