Merge ar1 [ ] and ar2 [ ] with O ( 1 ) extra space
static int arr1 [ ] = new int [ ] { 1 , 5 , 9 , 10 , 15 , 20 } ; static int arr2 [ ] = new int [ ] { 2 , 3 , 8 , 13 } ; static void merge ( int m , int n ) {