How do you solve Check if Numbers Are Ascending in a Sentence on LeetCode?

Check if Numbers Are Ascending in a Sentence (LeetCode #2042) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Extracting numbers while iterating saves space and time.

What is the brute force solution for Check if Numbers Are Ascending in a Sentence?

The brute force approach for Check if Numbers Are Ascending in a Sentence is Brute Force, with O(n²) time complexity and O(n) space complexity. The brute-force approach involves extracting all tokens from the sentence and checking each number against the next one to see if they are strictly increasing. This is straightforward but inefficient as it requires multiple comparisons. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Check if Numbers Are Ascending in a Sentence?

Check if Numbers Are Ascending in a Sentence uses the following concepts: String. The recommended patterns to study are: String Manipulation, Array Traversal.

What are the interview tips for Check if Numbers Are Ascending in a Sentence?

Always clarify the problem statement before jumping to code. Think about edge cases, such as sentences with no numbers or all equal numbers. Explain your thought process as you code; it shows understanding.

What are common mistakes when solving Check if Numbers Are Ascending in a Sentence?

Not handling the case where numbers are equal. Confusing the comparison operators (using <= instead of <).

#2042

Check if Numbers Are Ascending in a Sentence

Easy

StringString ManipulationArray Traversal

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(n)	O(1)

💡

Intuition

Time O(n)Space O(1)

The optimal solution improves efficiency by checking numbers as we extract them, avoiding the need to store all numbers. This allows us to compare each number with the last one directly, reducing the number of comparisons.

⚙️

Algorithm

6 steps

1Step 1: Split the sentence into tokens using spaces.
2Step 2: Initialize a variable to keep track of the last number found, starting at -1 (since numbers are positive).
3Step 3: Iterate through each token, and if it's a number, convert it and compare it with the last number.
4Step 4: If the current number is not greater than the last number, return false.
5Step 5: Update the last number to the current number and continue.
6Step 6: If the loop completes, return true.

solution.py12 lines

1# Full working Python code
2
3def are_numbers_ascending(s):
4    tokens = s.split()
5    last_number = -1
6    for token in tokens:
7        if token.isdigit():
8            current_number = int(token)
9            if current_number <= last_number:
10                return False
11            last_number = current_number
12    return True

ℹ

Complexity note: The time complexity is O(n) because we only pass through the tokens once. The space complexity is O(1) since we only use a few variables to keep track of the last number.

1Extracting numbers while iterating saves space and time.
2Strictly increasing means no equal numbers are allowed.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.