String to Integer (atoi)

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Solution Guide: String to Integer (atoi)

Approach

Skip leading spaces, parse an optional sign, read contiguous digits, and clamp overflow to the 32-bit signed integer range.

Complexity Analysis

Time
O(n)
Space
O(1)

Pattern

String Parsing

Why It Works

The parser follows the exact deterministic token order required by the specification and safely caps out-of-range values.

Updated Feb 2026