fix(QuickSort): use low instead of hardcoded 0 in left recursive call (#2)

The left recursive call passed a hardcoded 0 as the lower bound instead
of low, so every left-partition call re-sorted the array from index 0
rather than from the start of the current sub-problem. The result stayed
correct (the [0, low-1] prefix is already in place) but recursion work
blew up to O(n^2): on a descending array of 2000 elements the buggy
version makes 1,001,001 quickSort invocations vs 3,999 after the fix,
which is what can drive the reported StackOverflowError on large inputs.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: omprashantjain

4 Other Problems/QuickSort.java

@@ -26,7 +26,7 @@ private void quickSort(int[] nums, int low,
     if (low < high) {
       int partitionIndex = partition(nums, low,
           high);
-      quickSort(nums, 0, partitionIndex - 1);
+      quickSort(nums, low, partitionIndex - 1);
       quickSort(nums, partitionIndex + 1, high);
     }
   }