// use k scan array, and keep 2 more pointers i and j
// element in [0,i] < key
// element in (i,j] == key
// element in (j,k] > key
public static void partition3Way(int[] A, int key) {
int i = -1;
int j = -1;
for (int k = 0; k < A.length; k++) {
if (A[k] > key) continue;
else if (A[k] == key) ArrayUtil.swap(A, k, ++j);
else {
if (j == i) j = i + 1; // no elements equals to key
ArrayUtil.swap(A, k, ++i);
if (A[k] == key) ArrayUtil.swap(A, k, ++j); // swap back if prev swap put equal element to k
}
}
}
public static int partitionArray(int[] nums, int k) {
// write your code here
int i = -1;
for (int j = 0; j < nums.length; j++) {
if (nums[j] < k) ArrayUtil.swap(nums, ++i, j);
}
return i + 1;
}