#434

Easy

auto_awesomeString-driven solution strategy

LeetCode Problem Workspace

Number of Segments in a String

Count the segments of non-space characters in a string by applying a string-driven approach to solve the problem.

Problem Statement

Given a string s, you need to return the number of segments in the string. A segment is defined as a contiguous sequence of non-space characters. Spaces are used to separate different segments.

For example, for the string "Hello, my name is John", there are 5 segments: ["Hello,", "my", "name", "is", "John"]. Spaces between these segments do not count as segments themselves.

Examples

Example 1

Input: s = "Hello, my name is John"

Output: 5

The five segments are ["Hello,", "my", "name", "is", "John"]

Example 2

Input: s = "Hello"

Output: 1

Example details omitted.

Constraints

0 <= s.length <= 300
s consists of lowercase and uppercase English letters, digits, or one of the following characters "!@#$%^&*()_+-=',.:".
The only space character in s is ' '.

Solution Approach

Iterate Through the String

A straightforward approach is to iterate through each character in the string. Start by skipping spaces, then count consecutive non-space characters as a single segment when a space is encountered or the string ends.

Split the String by Spaces

Split the input string using spaces as delimiters. After the split, any empty parts resulting from multiple spaces should be ignored. Count the remaining non-empty segments.

Use Regular Expressions

Use regular expressions to find sequences of non-space characters. This can simplify the counting of segments, especially when multiple spaces are present.

Complexity Analysis

Metric	Value
Time	Depends on the final approach
Space	Depends on the final approach

The time complexity depends on the approach. Iterating through the string or splitting by spaces typically takes linear time, O(n), where n is the length of the string. Using regular expressions might add some overhead, but still remains O(n). The space complexity is O(1) for the iterative approach, but O(n) when splitting the string.

What Interviewers Usually Probe

Candidate demonstrates a clear understanding of how to handle spaces and non-space characters in the string.
Candidate uses an efficient strategy to avoid unnecessary operations, such as splitting on all spaces.
Candidate can explain how to optimize for edge cases, such as leading, trailing, or multiple spaces.

Common Pitfalls or Variants

Common pitfalls

Not handling leading or trailing spaces correctly, which might lead to inaccurate segment counts.
Forgetting to exclude empty segments when splitting the string, especially when multiple spaces are used.
Using inefficient methods like repeatedly scanning the string for spaces instead of processing the string in a single pass.

Follow-up variants

The input string contains leading or trailing spaces.
The input string contains multiple consecutive spaces.
The input string is empty or consists only of spaces.

FAQ

What is the key strategy for solving the 'Number of Segments in a String' problem?

The key strategy is to process the string efficiently by counting contiguous sequences of non-space characters, ensuring that spaces don't contribute to the segment count.

How do I handle multiple spaces in the 'Number of Segments in a String' problem?

When splitting the string by spaces, ignore any resulting empty segments caused by multiple spaces between words.

What is the time complexity of solving the 'Number of Segments in a String' problem?

The time complexity is generally O(n), where n is the length of the string. Both the iterative approach and splitting by spaces operate in linear time.

Can the 'Number of Segments in a String' problem be solved using regular expressions?

Yes, regular expressions can be used to identify and count sequences of non-space characters efficiently.

What should I avoid when solving the 'Number of Segments in a String' problem?

Avoid unnecessary operations like scanning the string repeatedly. It's best to handle the string in one pass or use efficient methods like splitting and regular expressions.

terminal

Solution

Solution 1: String Splitting

We split the string $\textit{s}$ by spaces and then count the number of non-empty words.

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class Solution:
    def countSegments(self, s: str) -> int:
        return len(s.split())

Solution 2: Simulation

We can also directly traverse each character $\text{s[i]}$ in the string. If $\text{s[i]}$ is not a space and $\text{s[i-1]}$ is a space or $i = 0$, then $\text{s[i]}$ marks the beginning of a new word, and we increment the answer by one.

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class Solution:
    def countSegments(self, s: str) -> int:
        return len(s.split())

Continue Practicing

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