PROBLEM DESCRIPTION
Given an array arr[], its starting position l and its ending position r. Sort the array using merge sort algorithm.
SOLUTION
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class Solution
{
void merge(int arr[], int l, int m, int r)
{
int[] out = new int[r-l+1];
int i = l;
int j = m+1;
int idx = 0;
while(i<=m && j<=r){
if(arr[i] < arr[j]){
out[idx++] = arr[i++];
}else{
out[idx++] = arr[j++];
}
}
while(i <= m)
out[idx++] = arr[i++];
while(j <= r)
out[idx++] = arr[j++];
for(int k=0; k<out.length; k++){
arr[k+l] = out[k];
}
}
void mergeSort(int arr[], int l, int r)
{
if( l >= r)
return;
int m = l + (r-l) / 2;
mergeSort(arr, l, m);
mergeSort(arr, m+1, r);
merge(arr, l, m, r);
}
}