<p>Given an integer array <code>nums</code>, return <em>the maximum difference between two successive elements in its sorted form</em>. If the array contains less than two elements, return <code>0</code>.</p>

<p>You must write an algorithm that runs in linear time and uses linear extra space.</p>

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

<pre>
<strong>Input:</strong> nums = [3,6,9,1]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The sorted form of the array is [1,3,6,9], either (3,6) or (6,9) has the maximum difference 3.
</pre>

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

<pre>
<strong>Input:</strong> nums = [10]
<strong>Output:</strong> 0
<strong>Explanation:</strong> The array contains less than 2 elements, therefore return 0.
</pre>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    int maximumGap(vector<int>& nums) {
        if (nums.size() <= 1)
            return 0;
        
        // Find maximum
        int max = *std::max_element(nums.cbegin(), nums.cend());
        int n_digits = (max == 0) ? 1 : 0;
        while (max > 0) {
            max /= 10;
            n_digits++;
        }
        std::cout << "n_digits == " << n_digits << std::endl;
        
        // Radix sort
        std::vector<std::vector<int>> buckets;
        buckets.reserve(10);
        for (int i = 0; i < 10; i++) {
            buckets.push_back({});
        }
        for (int digit = 0; digit < n_digits; digit++) {
            // Iterate over nums, place in buckets
            for (const auto& num : nums) {
                // Extract digit-th digit from num
                int temp = num;
                for (int i = 0; i < digit; i++)
                    temp /= 10;
                int digit_val_of_num = temp % 10;
                // Append to corresponding bucket
                buckets[digit_val_of_num].push_back(num);
            }
            // Move from buckets to nums
            nums.clear();
            for (const auto& bucket : buckets) {
                for (const auto& el : bucket) {
                    nums.push_back(el);
                }
            }
            // Clear buckets
            for (auto& bucket : buckets) {
                bucket.clear();
            }
        }
        for (const auto& num : nums) {
            std::cout << num << std::endl;
        }
        
        // nums is sorted, solve question
        int max_gap = 0;
        for (int i = 1; i < nums.size(); i++) {
            max_gap = std::max(max_gap, nums[i] - nums[i-1]);
        }
        return max_gap;
    }
};
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