void merge_sort(VInt& arr, int p, VInt& sarr)
{
int len = arr.size();
int leftLen = p ;
int rightLen = len - p;
VInt leftSorted;
VInt rightSorted;
//cout<<"ll "<<leftLen<<"rl "<<rightLen<<endl;
if(leftLen > 1) {
VInt larr(arr.begin(), arr.begin() + p);
merge_sort(larr,leftLen/2, leftSorted);
} else{
//cout<<"only one left"<<endl;
leftSorted.push_back(arr[0]);
}
if(rightLen > 1) {
VInt rarr(arr.begin() + p, arr.end());
merge_sort(rarr,rightLen/2, rightSorted);
} else {
//cout<<"only one right"<<endl;
rightSorted.push_back(arr[1]);
}
combine(leftSorted, rightSorted, sarr);
}
void combine(VInt& l, VInt& r, VInt& output)
{
int i = 0;
int j = 0;
while( i < l.size() && j < r.size()) {
if(l[i] < r[j]) {
output.push_back(l[i++]);
} else {
output.push_back(r[j++]);
}
}
VIter o_end = output.end();
if( i < l.size()) {
output.insert(o_end, l.begin()+ i, l.end());
} else {
output.insert(o_end, r.begin() + j, r.end());
}
}