Equal Sum Arrays With Minimum Number of Operations
<p>You are given two arrays of integers <code>nums1</code> and <code><font face="monospace">nums2</font></code>, possibly of different lengths. The values in the arrays are between <code>1</code> and <code>6</code>, inclusive.</p>

<p>In one operation, you can change any integer&#39;s value in <strong>any </strong>of the arrays to <strong>any</strong> value between <code>1</code> and <code>6</code>, inclusive.</p>

<p>Return <em>the minimum number of operations required to make the sum of values in </em><code>nums1</code><em> equal to the sum of values in </em><code>nums2</code><em>.</em> Return <code>-1</code>​​​​​ if it is not possible to make the sum of the two arrays equal.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,2,3,4,5,6], nums2 = [1,1,2,2,2,2]
<strong>Output:</strong> 3
<strong>Explanation:</strong> You can make the sums of nums1 and nums2 equal with 3 operations. All indices are 0-indexed.
- Change nums2[0] to 6. nums1 = [1,2,3,4,5,6], nums2 = [<u><strong>6</strong></u>,1,2,2,2,2].
- Change nums1[5] to 1. nums1 = [1,2,3,4,5,<strong><u>1</u></strong>], nums2 = [6,1,2,2,2,2].
- Change nums1[2] to 2. nums1 = [1,2,<strong><u>2</u></strong>,4,5,1], nums2 = [6,1,2,2,2,2].
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,1,1,1,1,1,1], nums2 = [6]
<strong>Output:</strong> -1
<strong>Explanation:</strong> There is no way to decrease the sum of nums1 or to increase the sum of nums2 to make them equal.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [6,6], nums2 = [1]
<strong>Output:</strong> 3
<strong>Explanation:</strong> You can make the sums of nums1 and nums2 equal with 3 operations. All indices are 0-indexed. 
- Change nums1[0] to 2. nums1 = [<strong><u>2</u></strong>,6], nums2 = [1].
- Change nums1[1] to 2. nums1 = [2,<strong><u>2</u></strong>], nums2 = [1].
- Change nums2[0] to 4. nums1 = [2,2], nums2 = [<strong><u>4</u></strong>].
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums1.length, nums2.length &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= nums1[i], nums2[i] &lt;= 6</code></li>
</ul>
Greedy; Array; Hash Table; Counting
class Solution {
    public int minOperations(int[] nums1, int[] nums2) {
        int s1 = Arrays.stream(nums1).sum();
        int s2 = Arrays.stream(nums2).sum();
        if (s1 == s2) {
            return 0;
        }
        if (s1 > s2) {
            return minOperations(nums2, nums1);
        }
        int d = s2 - s1;
        int[] arr = new int[nums1.length + nums2.length];
        int k = 0;
        for (int v : nums1) {
            arr[k++] = 6 - v;
        }
        for (int v : nums2) {
            arr[k++] = v - 1;
        }
        Arrays.sort(arr);
        for (int i = 1, j = arr.length - 1; j >= 0; ++i, --j) {
            d -= arr[j];
            if (d <= 0) {
                return i;
            }
        }
        return -1;
    }
}