String to Integer atoi in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the atoi function do?

It converts a string representing a number into its integer form, handling optional signs and ignoring leading spaces.

beginner

How does atoi handle leading spaces in the input string?

It skips all leading spaces before processing the number.

intermediate

What should atoi do if the string contains non-digit characters after the number?

It stops parsing at the first non-digit character and returns the integer parsed so far.

intermediate

How does atoi handle integer overflow?

It clamps the result to the 32-bit signed integer range: from -2,147,483,648 to 2,147,483,647.

beginner

What is the significance of the sign character in atoi?

A '+' or '-' sign before digits determines if the resulting integer is positive or negative.

What should atoi return for the input string " -42abc"?

A 42

B 0

C -420

D -42

Leading spaces are ignored, '-' sign is read, digits '42' parsed, stops at 'a'. Result is -42.

If the input string is "4193 with words", what does atoi return?

A 0

B 4193

C 4193 with words

D -4193

Parsing stops at first non-digit after digits. Returns 4193.

What happens if the input string is "words and 987"?

A 0

B 987

C words

D -987

No valid number at start, so returns 0.

How does atoi handle the input "-91283472332"?

A 0

B -91283472332

C -2147483648

D 2147483647

Number is less than INT_MIN, so clamps to -2147483648.

What is the first step atoi performs on the input string?

A Skip leading spaces

B Parse digits

C Check for overflow

D Return 0

First it skips all leading spaces before parsing sign or digits.

Explain step-by-step how atoi converts the string " -123abc" to an integer.

Think about how the function reads characters one by one.

Describe how atoi handles integer overflow and why it is important.

Consider what happens if the number is too big or too small.