Create 307. Range Sum Query - Mutable.cpp

Author: wargraver

Leetcode/Merge Sort/307. Range Sum Query - Mutable.cpp

@@ -0,0 +1,67 @@
+int diff; 
+vector<int> vect;
+int buildtree(int i,int st,int en,vector<int> nums){
+        if(st==en) return vect[i] = nums[st];
+        else if(st>en) return 0;
+        else{
+            int mid = (st+en)/2;
+            vect[i] = buildtree(2*i+1,st,mid,nums) +  buildtree(2*i+2,mid+1,en,nums);
+            return vect[i];
+        }
+    }
+int get_sum(int i,int st,int en,int left,int right){
+    if(st>en) return 0;
+    else if(st>right || en<left) return 0;
+    else{
+        if(st>=left && en<=right) return vect[i];
+        else{
+            int mid = (st+en)/2;
+            return get_sum(2*i+1,st,mid,left,right) + get_sum(2*i+2,mid+1,en,left,right);
+        }
+    }
+}
+void get_updated(int i,int st,int en,int index,int val){
+    if(st>en) return;
+    else if(st==en && st==index){
+        diff = val-vect[i];
+        vect[i] = val;
+        return;
+    }
+    else{
+        if(st>index || en<index) return;
+        else{
+            int mid = (st+en)/2;
+            get_updated(2*i+1,st,mid,index,val);
+            get_updated(2*i+2,mid+1,en,index,val);
+            vect[i] = vect[i]+diff;
+        }
+    }
+}
+class NumArray {
+public:
+    int cap;
+    NumArray(vector<int>& nums) {
+        int m = nums.size();
+        vect.clear();
+        for(int i=0;i<=4*m;i++) vect.push_back(0);
+        int st=0,en=m-1;
+        this->cap=en;diff=0;
+        buildtree(0,st,en,nums);
+    }
+    void update(int index, int val) {
+         int st=0,en=this->cap;
+        get_updated(0,st,en,index,val);
+    }
+    
+    int sumRange(int left, int right) {
+        int st=0,en=this->cap;
+        return get_sum(0,st,en,left,right);
+    }
+};
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * NumArray* obj = new NumArray(nums);
+ * obj->update(index,val);
+ * int param_2 = obj->sumRange(left,right);
+ */