Range Updates/Range Queries with BIT

#include <cstdio>
#include <cstring>
#define LSOne(S) (S & (-S))
using namespace std;

typedef long long ll;

// B1 and B2 are two fenwick trees
// Original array entries are assumed to be 0
// and only updates are stored.
ll B1[100005], B2[100005];

// Array size
int N;

// Point query
// Returns value at position b in the array for ft = B1
// Returns value to be subtracted from query(B1, b) * b for ft = B2
ll query(ll* ft, int b) {
    ll sum = 0;
    for (; b; b -= LSOne(b)) sum += ft[b];
    return sum;
}

// Range query: Returns the sum of all elements in [1...b]
ll query(int b) {
    return query(B1, b) * b - query(B2, b);
}

// Range query: Returns the sum of all elements in [i...j]
ll range_query(int i, int j)    {
    return query(j) - query(i - 1);
}

// Point update: Adds v to the value at position k in the array
// ft is the fenwick tree which represents that array
void update(ll* ft, int k, ll v) {
    for (; k <= N; k += LSOne(k)) ft[k] += v;
}

// Range update: Adds v to each element in [i...j]
void range_update(int i, int j, ll v)   {
    update(B1, i, v);
    update(B1, j + 1, -v);
    update(B2, i, v * (i - 1));
    update(B2, j + 1, -v * j);
}

int main()  {
    int T, C, p, q, cmd;
    ll v;

    scanf("%d", &T);
    while (T--) {
        // C -> No. of operations
        scanf("%d %d", &N, &C);
        memset(B1, 0, (N+1) * sizeof(ll));
        memset(B2, 0, (N+1) * sizeof(ll));
        while (C--) {
            scanf("%d %d %d", &cmd, &p, &q);
            // cmd is 0 for a range update and 1 for a range query
            if (cmd == 0)   {
                        scanf("%lld", &v);
                        range_update(p, q, v);
            } else
                        printf("%lld\n", range_query(p, q));
        }
    }

    return 0;
}