public static void shuffleArray(long[] a) {
int n = a.length;
Random random = new Random();
random.nextInt();
for (int i = 0; i < n; i++) {
int change = i + random.nextInt(n - i);
swap(a, i, change);
}
}
/** Returns the index of the largest value in the array.
* In case of a tie, an the index is selected randomly.
*/
public static int maxIndex(int[] from, Random rand) {
assert rand != null;
int result = 0;
int maxCount = 0; // count of maximal element for a 1 item reservoir sample
for( int i = 1; i < from.length; ++i ) {
if( from[i] > from[result] ) {
result = i;
maxCount = 1;
} else if( from[i] == from[result] ) {
if( rand.nextInt(++maxCount) == 0 ) result = i;
}
}
return result;
}