MO s algorithm

int block;

struct Query{
    int L, R, idx;
} q[mx];

bool compare(Query x, Query y){
    if (x.L/block != y.L/block)
        return x.L/block < y.L/block;
    return x.R < y.R;
}

void queryResults(int n, int m){
    block = (int)sqrt(n);

    sort(q, q + m, compare);
    int currL = 0, currR = 0;
    int currSum = 0;
    for (int i=0; i<m; i++){
        int L = q[i].L, R = q[i].R;
        while (currL < L){
            currSum -= a[currL];
            currL++;
        }
        while (currL > L){
            currSum += a[currL-1];
            currL--;
        }
        while (currR <= R){
            currSum += a[currR];
            currR++;
        }
        while (currR > R+1){
            currSum -= a[currR-1];
            currR--;
        }
    }
}