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This is a medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Google.

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

Solve Two Coding Interview Problems | Google Coding Question

Quick Overview

This question evaluates proficiency in parsing and expression evaluation, recursion/stack management, and string-processing for nested function-style arithmetic, alongside graph modeling, geometric distance reasoning, and traversal algorithms for the bomb chain-reaction scenario; the category is Coding & Algorithms.

Solve Two Coding Interview Problems

Company: Google

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

You are asked to solve two independent coding problems. ### Problem 1: Evaluate Nested Math Expressions Implement a function that evaluates a string expression containing nested function-style arithmetic calls. Supported operations: - `add(a, b)`: returns `a + b` - `sub(a, b)`: returns `a - b` Operands may be integers or nested expressions. Whitespace may appear anywhere and should be ignored. Examples: ```text Input: "add(1, sub(1, 0))" Output: 2 Input: "sub(add(3, 4), sub(10, 6))" Output: 3 ``` Requirements: - Parse and evaluate the expression correctly. - Support nested expressions of arbitrary depth within reasonable stack limits. - Handle multi-digit and negative integers if they appear. ### Problem 2: Compute Maximum Chain Reaction You are given a list of bombs. Each bomb is represented as `[x, y, r]`, where `(x, y)` is its position on a 2D plane and `r` is its blast radius. If bomb `i` explodes, it will trigger bomb `j` if the Euclidean distance between their centers is less than or equal to `i`'s radius. Triggered bombs explode immediately and may trigger more bombs. Return the maximum number of bombs that can explode if you choose exactly one bomb to detonate initially. Example: ```text Input: bombs = [[0,0,2], [2,0,2], [5,0,1]] Output: 2 Explanation: Detonating bomb 0 triggers bomb 1, but neither bomb can trigger bomb 2. ``` Requirements: - Model the chain reactions correctly. - Avoid floating-point precision issues when comparing distances. - Return the largest number of bombs reachable from any starting bomb.

Quick Answer: This question evaluates proficiency in parsing and expression evaluation, recursion/stack management, and string-processing for nested function-style arithmetic, alongside graph modeling, geometric distance reasoning, and traversal algorithms for the bomb chain-reaction scenario; the category is Coding & Algorithms.

Part 1: Evaluate Nested Math Expressions

Given a string expression, evaluate its value. The expression may be a single integer or a nested function-style arithmetic call using add(a, b) and sub(a, b). Operands can be integers or other nested expressions. Whitespace may appear anywhere and must be ignored. Support multi-digit and negative integers.

Constraints

1 <= len(expression) <= 100000
The input expression is syntactically valid
Integers may be negative and may contain multiple digits
All intermediate and final results fit in a signed 64-bit integer

Examples

Input: "add(1, sub(1, 0))"

Expected Output:

Explanation: sub(1, 0) = 1, then add(1, 1) = 2.

Input: "sub(add(3, 4), sub(10, 6))"

Expected Output:

Explanation: add(3, 4) = 7 and sub(10, 6) = 4, so 7 - 4 = 3.

Input: "sub(-5, add(-2, 3))"

Expected Output:

Explanation: add(-2, 3) = 1, then -5 - 1 = -6.

Input: " -15 "

Expected Output:

Explanation: Edge case: the entire expression is just a single negative integer with surrounding whitespace.

Hints

Think of the expression as a simple grammar: an expression is either an integer or an operator followed by two expressions inside parentheses.
Use a shared index while parsing so each character is processed only once.

Part 2: Compute Maximum Chain Reaction

You are given a list of bombs, where each bomb is [x, y, r]. If bomb i explodes, it triggers bomb j when the Euclidean distance between their centers is less than or equal to bomb i's radius. Triggered bombs explode immediately and may trigger more bombs. Return the maximum number of bombs that can explode if you choose exactly one bomb to detonate first.

Constraints

0 <= len(bombs) <= 100
-10^9 <= x, y <= 10^9
0 <= r <= 10^9
Use integer arithmetic when comparing distances to avoid floating-point precision issues

Examples

Input: [[0, 0, 2], [2, 0, 2], [5, 0, 1]]

Expected Output:

Explanation: Bomb 0 can trigger bomb 1, but bomb 2 is too far away from both.

Input: [[0, 0, 4], [3, 0, 3], [6, 0, 3], [9, 0, 1]]

Expected Output:

Explanation: Starting from bomb 0 or bomb 1 can trigger the entire chain of four bombs.

Input: []

Expected Output:

Explanation: Edge case: no bombs means no explosions.

Input: [[1, 1, 0]]

Expected Output:

Explanation: Edge case: a single bomb always counts as one exploded bomb.

Input: [[0, 0, 0], [0, 0, 0]]

Expected Output:

Explanation: Even with zero radius, bombs at the exact same position can trigger each other because the distance is 0.

Hints

Treat each bomb as a node in a directed graph, with an edge from i to j if i can directly trigger j.
Compare squared distances with squared radii so you never need to use square roots.

Quick Overview