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This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Asana.

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This question is commonly asked for Software Engineer candidates at Asana during technical interviews.

Implement ASCII canvas and solve two data problems

Quick Overview

This multi-part question evaluates implementation and algorithmic competencies such as managing a mutable ASCII canvas and rendering, in-place array algorithms for the product-excluding-self problem under O(n) time and O(1) extra space, and external-memory parsing and frequency counting for very large log files, including correctness and edge-case handling. It is commonly asked because it tests practical coding ability, correctness under resource constraints, parsing/IO trade-offs and complexity reasoning; the category is Coding & Algorithms with file/systems aspects, and the level of abstraction spans practical implementation and conceptual algorithmic understanding.

Implement ASCII canvas and solve two data problems

Company: Asana

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

Solve the following coding tasks. 1) **ASCII Canvas / Printer** Implement a small drawing engine for a fixed-size canvas of **width = 10** and **height = 6**. - Each cell stores: - an ASCII character (e.g., 'A', '#', or space) - an optional color (you can model it as an enum/string; exact coloring output is not important unless you choose to render it) - Implement these operations: - `draw_rectangle(char ch, int leftX, int topY, int rightX, int bottomY)` - Draw a filled rectangle within inclusive coordinates. - `drag_and_drop(int selectX, int selectY, int toX, int toY)` - Move the selected cell’s content to the destination. - **Do not change layer order** (assume there are no layers; treat it as moving that single cell’s content). - Define what happens to the source and destination cells. - `erase_area(int fromX, int toX, int fromY, int toY)` - Clear all cells in the area. - Provide a way to render/print the canvas as ASCII. - Discuss edge cases (out-of-bounds coordinates, overlapping operations, empty selections). 2) **Array product excluding self** Given an integer array `nums`, return an array `out` where `out[i]` equals the product of all `nums[j]` for `j != i`. - Do **not** use division. - Target `O(n)` time. - Extra space should be `O(1)` beyond the output array. - Handle zeros correctly. 3) **Count IP occurrences in large log files** You have a very large local log file where each line contains an IP address (possibly with other text). - Compute how many times each IP occurs. - Consider that the file may not fit in memory. - Discuss parsing/validation edge cases and performance tradeoffs.

Quick Answer: This multi-part question evaluates implementation and algorithmic competencies such as managing a mutable ASCII canvas and rendering, in-place array algorithms for the product-excluding-self problem under O(n) time and O(1) extra space, and external-memory parsing and frequency counting for very large log files, including correctness and edge-case handling. It is commonly asked because it tests practical coding ability, correctness under resource constraints, parsing/IO trade-offs and complexity reasoning; the category is Coding & Algorithms with file/systems aspects, and the level of abstraction spans practical implementation and conceptual algorithmic understanding.

Part 1: Fixed ASCII Canvas Renderer

Implement a tiny 10 x 6 ASCII drawing engine. The canvas starts empty. You will apply rectangle, move, and erase operations, then return the rendered canvas. For this coding version, each cell stores only a character; color can be ignored. Rectangle coordinates are inclusive. A move transfers exactly one cell: the destination is overwritten and the source becomes empty. If a move selects an empty cell, nothing happens.

Constraints

Canvas size is fixed: width = 10 and height = 6.
0 <= number of operations <= 10^5.
For 'rect', ch is a single ASCII character.
For 'rect' and 'erase', normalize reversed coordinates and clip to the canvas.
For 'move', if source or destination is out of bounds, ignore the operation.

Examples

Input: []

Expected Output: ['..........', '..........', '..........', '..........', '..........', '..........']

Explanation: Edge case: no operations leaves the canvas empty.

Input: [('rect', '#', 1, 1, 3, 2)]

Expected Output: ['..........', '.###......', '.###......', '..........', '..........', '..........']

Explanation: Draws a filled 3 x 2 rectangle using inclusive coordinates.

Input: [('rect', 'A', 0, 0, 0, 0), ('rect', 'B', 2, 0, 2, 0), ('move', 0, 0, 2, 0)]

Expected Output: ['..A.......', '..........', '..........', '..........', '..........', '..........']

Explanation: The A at (0,0) moves to (2,0), overwriting B, and the source becomes empty.

Input: [('rect', 'X', -2, -1, 2, 1), ('erase', 1, 0, 1, 0)]

Expected Output: ['..X.......', '..X.......', '..........', '..........', '..........', '..........']

Explanation: The rectangle is clipped to the canvas, then the erase area uses reversed coordinates and clears the left two columns.

Hints

A 2D list of characters is enough because the canvas size never changes.
Before drawing or erasing, sort the x values and y values, then clip them to the valid range.

Part 2: Product of Array Except Self

Given an integer array nums, return an array out where out[i] is the product of every element in nums except nums[i]. Do not use division. Your algorithm must run in O(n) time and use O(1) extra space beyond the returned output array.

Constraints

0 <= len(nums) <= 10^5.
-30 <= nums[i] <= 30.
Do not use division.
Use only O(1) extra space beyond the output array.

Examples

Input: []

Expected Output: []

Explanation: Edge case: an empty array returns an empty array.

Input: [5]

Expected Output: [1]

Explanation: With one element, the product of all other elements is the empty product, which is 1.

Input: [1, 2, 3, 4]

Expected Output: [24, 12, 8, 6]

Explanation: Standard example using prefix and suffix products.

Input: [0, 1, 2, 3]

Expected Output: [6, 0, 0, 0]

Explanation: Only the position containing 0 gets the product of the non-zero values.

Input: [0, 0, 5]

Expected Output: [0, 0, 0]

Explanation: With two zeros, every position has at least one zero in its product.

Hints

For each position, you need the product of everything to its left and everything to its right.
You can store prefix products directly in the output array, then multiply by a running suffix product in a backward pass.

Part 3: Count Valid IPv4 Addresses in Log Lines

You are given log lines that simulate a large file. Count how many times each valid IPv4 address appears anywhere in the text. Process the lines one by one rather than combining them into one giant string. Return the final counts sorted by numeric IP address ascending. A valid IPv4 address has exactly four decimal octets, each from 0 to 255, and no leading zeros unless the octet is exactly 0. If a line contains the same IP multiple times, count every occurrence.

Constraints

0 <= len(lines) <= 10^5 in tests.
The total number of characters can be large, so scan line by line.
Valid IPv4 format is a.b.c.d with exactly 4 octets.
Each octet must be in [0, 255].
Octets with leading zeros, such as 01 or 001, are invalid unless the octet is exactly 0.
For this coding task, assume the final set of distinct valid IPs fits in memory.

Examples

Input: ['src=10.0.0.1 dst=192.168.1.2', 'retry from 10.0.0.1', 'mirror 10.0.0.1']

Expected Output: [('10.0.0.1', 3), ('192.168.1.2', 1)]

Explanation: The IP 10.0.0.1 appears three times, and 192.168.1.2 appears once.

Input: ['bad 256.1.1.1 good 1.2.3.4', 'skip 01.2.3.4 and 1.2.3', 'also 1.2.3.4.5 no']

Expected Output: [('1.2.3.4', 1)]

Explanation: 256.1.1.1 is out of range, 01.2.3.4 has a leading zero, 1.2.3 has too few parts, and 1.2.3.4.5 has too many parts.

Input: ['0.0.0.0 255.255.255.255 0.0.0.0']

Expected Output: [('0.0.0.0', 2), ('255.255.255.255', 1)]

Explanation: Both boundary IPs are valid, and 0.0.0.0 appears twice.

Input: []

Expected Output: []

Explanation: Edge case: no lines means no IP occurrences.

Hints

First extract digit-and-dot runs from each line, then validate which ones are exactly 4 octets.
A hash map is enough for counting; sort only once at the end.

Last updated: May 1, 2026

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Quick Overview

Implement ASCII canvas and solve two data problems

Company: Asana

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

Part 1: Fixed ASCII Canvas Renderer

Constraints

Canvas size is fixed: width = 10 and height = 6.
0 <= number of operations <= 10^5.
For 'rect', ch is a single ASCII character.
For 'rect' and 'erase', normalize reversed coordinates and clip to the canvas.
For 'move', if source or destination is out of bounds, ignore the operation.

Examples

Input: []

Expected Output: ['..........', '..........', '..........', '..........', '..........', '..........']

Explanation: Edge case: no operations leaves the canvas empty.

Input: [('rect', '#', 1, 1, 3, 2)]

Expected Output: ['..........', '.###......', '.###......', '..........', '..........', '..........']

Explanation: Draws a filled 3 x 2 rectangle using inclusive coordinates.

Input: [('rect', 'A', 0, 0, 0, 0), ('rect', 'B', 2, 0, 2, 0), ('move', 0, 0, 2, 0)]

Expected Output: ['..A.......', '..........', '..........', '..........', '..........', '..........']

Explanation: The A at (0,0) moves to (2,0), overwriting B, and the source becomes empty.

Input: [('rect', 'X', -2, -1, 2, 1), ('erase', 1, 0, 1, 0)]

Expected Output: ['..X.......', '..X.......', '..........', '..........', '..........', '..........']

Explanation: The rectangle is clipped to the canvas, then the erase area uses reversed coordinates and clears the left two columns.

Hints

A 2D list of characters is enough because the canvas size never changes.
Before drawing or erasing, sort the x values and y values, then clip them to the valid range.

Part 2: Product of Array Except Self

Constraints

0 <= len(nums) <= 10^5.
-30 <= nums[i] <= 30.
Do not use division.
Use only O(1) extra space beyond the output array.

Examples

Input: []

Expected Output: []

Explanation: Edge case: an empty array returns an empty array.

Input: [5]

Expected Output: [1]

Explanation: With one element, the product of all other elements is the empty product, which is 1.

Input: [1, 2, 3, 4]

Expected Output: [24, 12, 8, 6]

Explanation: Standard example using prefix and suffix products.

Input: [0, 1, 2, 3]

Expected Output: [6, 0, 0, 0]

Explanation: Only the position containing 0 gets the product of the non-zero values.

Input: [0, 0, 5]

Expected Output: [0, 0, 0]

Explanation: With two zeros, every position has at least one zero in its product.

Hints

For each position, you need the product of everything to its left and everything to its right.
You can store prefix products directly in the output array, then multiply by a running suffix product in a backward pass.

Part 3: Count Valid IPv4 Addresses in Log Lines

Constraints

0 <= len(lines) <= 10^5 in tests.
The total number of characters can be large, so scan line by line.
Valid IPv4 format is a.b.c.d with exactly 4 octets.
Each octet must be in [0, 255].
Octets with leading zeros, such as 01 or 001, are invalid unless the octet is exactly 0.
For this coding task, assume the final set of distinct valid IPs fits in memory.

Examples

Input: ['src=10.0.0.1 dst=192.168.1.2', 'retry from 10.0.0.1', 'mirror 10.0.0.1']

Expected Output: [('10.0.0.1', 3), ('192.168.1.2', 1)]

Explanation: The IP 10.0.0.1 appears three times, and 192.168.1.2 appears once.

Input: ['bad 256.1.1.1 good 1.2.3.4', 'skip 01.2.3.4 and 1.2.3', 'also 1.2.3.4.5 no']

Expected Output: [('1.2.3.4', 1)]

Explanation: 256.1.1.1 is out of range, 01.2.3.4 has a leading zero, 1.2.3 has too few parts, and 1.2.3.4.5 has too many parts.

Input: ['0.0.0.0 255.255.255.255 0.0.0.0']

Expected Output: [('0.0.0.0', 2), ('255.255.255.255', 1)]

Explanation: Both boundary IPs are valid, and 0.0.0.0 appears twice.

Input: []

Expected Output: []

Explanation: Edge case: no lines means no IP occurrences.

Hints

First extract digit-and-dot runs from each line, then validate which ones are exactly 4 octets.
A hash map is enough for counting; sort only once at the end.

Last updated: May 1, 2026

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