Software Engineer · Online Assessment · Coding

Uber — Software Engineer

Level: Junior-Level

Round: Online Assessment · Type: Coding · Difficulty: 6/10 · Duration: 60 min · Interviewer: Unfriendly

Topics: Arrays, Graphs, Depth-First Search, Stacks

Location: San Francisco, CA

Interview date: 2026-02-15

Summary

I had an online assessment with two questions.

Details

The online assessment included these two coding questions:

1. Price Discount: Given a prices array, find the first number to the right of each element that is smaller than the element itself. The difference between these two numbers is the discount. If there is no number smaller, no discount is applied.

2. Minimum Edge Reversal to Make All Edges Point Away from a Root:

Optimize a directed graph representing a neural network by selecting a root node that minimizes the number of edge reversals needed.

The graph has:

• n nodes, numbered from 1 to n
• n − 1 directed edges
• The i-th edge connects node g_from[i] to g_to[i]

Task

• Select any node as the root
• Reverse as many edges as necessary so that all edges flow away from the root
• Find the root node choice that requires the minimum number of edge reversals

Example

g_nodes = 4 g_from = [1, 2, 3] g_to = [4, 4, 4]

This means the directed edges are:

1 → 4 2 → 4 3 → 4

Explanation

If node 2 is selected as the root:

Edges 1 → 4 and 3 → 4 must be reversed

So they become:

4 → 1 4 → 3

Edge 2 → 4 already flows away from the root and does not need reversal

Minimum number of edges to invert = 2