fix: handle zero and negative numbers in RadixSort

[huizixin]

Bug Description

RadixSort.getLengthOfLongestElement() fails when the input array contains only zeros or negative numbers:

• Math.log10(0) returns -Infinity, causing numPasses to be -Infinity
• Math.log10(-N) returns NaN, causing numPasses to be NaN

In both cases, the sorting loop (for (let currentIndex = 0; currentIndex < numPasses; ...)) never executes, and the unsorted array is returned as-is.

Steps to Reproduce

const sorter = new RadixSort();
sorter.sort([-3, -1, -2]); // Returns [-3, -1, -2] (not sorted!)
sorter.sort([0, 0, 0]);    // Returns [0, 0, 0] (correct by accident)

Fix

Added an early return in getLengthOfLongestElement() to handle edge cases where the maximum value is 0 or negative:

getLengthOfLongestElement(array) {
    if (this.isArrayOfNumbers(array)) {
      const max = Math.max(...array);
      // Handle edge cases where max is 0 or negative
      if (max <= 0) return 1;
      return Math.floor(Math.log10(max)) + 1;
    }
    // ...
}

Testing

The existing test suite (SortTester.testSort) includes [3, 4, 2, 1, 0, 0, 4, 3, 4, 2] which works correctly. However, arrays of purely negative numbers are not tested and reveal this bug.

Note: Radix Sort has inherent limitations with negative numbers. A complete fix would require splitting the array by sign and merging results. This PR addresses the immediate NaN/-Infinity issue to prevent silent incorrect behavior.