I have an ArrayList of objects which I'm trying to sort by a 'saving'number stored in the object. My code so far is written below
public static void mergesort(ArrayList<Object> list){
if(list.size() > 1){
//Split the list in half and create an ArrayList for each side
int q = list.size()/2;
//System.out.println(list.size() + " " + q);
ArrayList<Object> leftList = new ArrayList<Object>();
for(int i = 0; i > q; i++){
leftList.add(list.get(i));
}
ArrayList<Object> rightList = new ArrayList<Object>();
for(int j = q; j < list.size(); j++){
rightList.add(list.get(j));
}
// System.out.println(" leftList " + leftList.size() + " rightList " + rightList.size());
//sort each half of the list
//note: this will happen recursively
mergesort(leftList);
mergesort(rightList);
merge(leftList, rightList, list);
}
}
public static void merge(ArrayList<Object> leftList, ArrayList<Object> rightList, ArrayList<Object> list){
//'i' stores the index of the main array
//'l' stores the index of the left array
//'r' stores the index of the right array
int i = 0, l = 0, r = 0;
//the loop will run until one of the arraylists becomes empty
while(leftList.size() != l && rightList.size() !=r){
//if the saving of the current element of leftList is less than the rightList saving
if(leftList.get(l).getSaving() < rightList.get(r).getSaving()){
//Copy the current element into the final array
list.set(i, leftList.get(l));
i++;
l++;
}
else {
list.set(i, rightList.get(r));
i++;
r++;
}
}
while(leftList.size() != l){
list.set(i, leftList.get(l));
i++;
l++;
}
while(rightList.size() != r){
list.set(i,rightList.get(r));
i++;
r++;
}
}
For some reason when I run it I don't get any errors, however, the list remains unsorted. any advice would be much appreciated. Thanks in advance
The problem is in the first for of the mergesort method:
for (int i = 0; i > q; i++) {
It should be:
for (int i = 0; i < q; i++) {
Checkout the condition..