Status: IN
A `0` element contributes nothing to `digit_sum` because the `while num > 0` loop body never executes for zero — correct under the LeetCode constraint `nums[i] >= 1` but would silently drop zeros if the constraint were relaxed.
Source: entries/2026/06/06/difference-between-element-sum-and-digit-sum-of-an-array-solution.md