Daily LeetCode – day0131 1775. Equal Sum Arrays With Minimum Number of Operations

// 1775. Equal Sum Arrays With Minimum Number of Operations
class Solution {
    public int minOperations(int[] nums1, int[] nums2) {
        if (nums1.length > nums2.length * 6 || nums2.length > nums1.length * 6) {
            return -1;
        }
        int[] frequency1 = new int[7];
        int[] frequency2 = new int[7];
        int sum1 = 0;
        int sum2 = 0;
        for (int num : nums1) {
            sum1 += num;
            ++frequency1[num];
        }
        for (int num : nums2) {
            sum2 += num;
            ++frequency2[num];
        }
        if (sum1 < sum2) {
            int t = sum2;
            sum2 = sum1;
            sum1 = t;
            int[] te = frequency1;
            frequency1 = frequency2;
            frequency2 = te;
        }
        int ans = 0;
        int change = 1;
        while (sum1 > sum2) {
            int diff = sum1 - sum2;
            if (frequency1[7 - change] * (6 - change) < diff) {
                int changeTimes = frequency1[7 - change];
                frequency1[7 - change] = 0;
                sum1 -= changeTimes * (6 - change);
                ans += changeTimes;
            } else {
                int changeTimes = diff / (6 - change);
                ans += changeTimes;
                if (diff % (6 - change) != 0) {
                    ++ans;
                }
                return ans;
            }
            diff = sum1 - sum2;
            if (frequency2[change] * (6 - change) < diff) {
                int changeTimes = frequency2[change];
                frequency2[change] = 0;
                sum2 += changeTimes * (6 - change);
                ans += changeTimes;
            } else {
                int changeTimes = diff / (6 - change);
                ans += changeTimes;
                if (diff % (6 - change) != 0) {
                    ++ans;
                }
                return ans;
            }

            ++change;
        }
        return ans;
    }
}

学习笔记：
这是一道计数、贪心算法的中等题。
先数出来，然后把小的一组的1变6，大的一组6变1，然后把小的一组2变6，大的一组5变1……
方法特别容易想到，但是写成代码总是很麻烦要考虑很多东西，写得也很繁琐。