Incorrect update elements in Fenwick Tree - fenwick-tree

Question

I wrote a program, which give an sum of range by getting command 's' and update an element by command 'u', but it works incorrect.
Help me please.
#include <iostream>
#include <vector>
#include <fstream>
using namespace std;
template <typename indexT, typename valueT> class FenwickTree{
public:
FenwickTree(vector<valueT> &buffer){
tree.resize(buffer.size());
for (indexT i = 0; i < buffer.size(); ++i)
update(i, buffer[i]);
}
valueT getSolution(const indexT l, const indexT r) const{
return getSolution(r) - getSolution(l - 1);
}
void update(indexT position, const valueT v){
valueT delta = v - tree[position];
for (indexT i = position; i < tree.size(); i = i | (i + 1))
tree[i] += delta;
}
private:
vector <valueT> tree;
valueT getSolution(const indexT r) const{
valueT result = 0;
for (indexT i = r; i >= 0; i = (i & (i + 1)) - 1)
result = tree[i] + result;
return result;
}
};
int main(){
ifstream file;
file.open("D:\\input.txt", ios::in);
unsigned long long n, k;
file >> n;
vector<long long> buffer(n);
for (long long i = 0; i < n; ++i)
file >> buffer[i];
file >> k;
FenwickTree<long long, long long> fenwickTree(buffer);
for (long long i = 0; i < k; ++i){
char command;
long long a, b;
file >> command >> a >> b;
if (command == 's')
cout << fenwickTree.getSolution(a - 1, b - 1) << " ";
else if (command == 'u')
fenwickTree.update(a - 1, b);
}
file.close();
return 0;
}
Correct work:
input:
10
613 263 312 670 216 142 976 355 488 370
10
s 2 7
s 4 8
u 7 969
u 1 558
s 2 7
u 2 731
s 4 9
s 1 3
u 8 76
u 5 377
output:
2579 2359 2572 2840 1601
I calculate a delta between new old and new value and then update fenwick tree, but it doesn't work for me.

Answer 1

Fixed it:
#include <iostream>
#include <vector>
#include <fstream>
using namespace std;
template <typename indexT, typename valueT> class FenwickTree{
public:
FenwickTree(vector<valueT> &buffer){
tree.resize(buffer.size());
for (indexT i = 0; i < buffer.size(); ++i)
update(i, buffer[i]);
}
valueT getSolution(const indexT l, const indexT r) const{
return getSolution(r) - getSolution(l - 1);
}
void update(indexT position, const valueT v){
for (indexT i = position; i < tree.size(); i = i | (i + 1))
tree[i] += v;
}
private:
vector <valueT> tree;
valueT getSolution(const indexT r) const{
valueT result = 0;
for (indexT i = r; i >= 0; i = (i & (i + 1)) - 1)
result += tree[i];
return result;
}
};
int main(){
ifstream file;
file.open("D:\\input.txt", ios::in);
unsigned long long n, k;
file >> n;
vector<long long> buffer(n);
for (long long i = 0; i < n; ++i)
file >> buffer[i];
file >> k;
FenwickTree<long long, long long> fenwickTree(buffer);
for (long long i = 0; i < k; ++i){
char command;
long long a, b;
file >> command >> a >> b;
if (command == 's')
cout << fenwickTree.getSolution(a - 1, b - 1) << " ";
else if (command == 'u'){
fenwickTree.update(a - 1, b - buffer[a - 1]);
buffer[a - 1] = b;
}
}
file.close();
int lal = 0;
cin >> lal;
return 0;
}