Check If Numbers are Ascending in a Sentence

Problem Description

A sentence is a list of tokens separated by a single space with no leading or trailing spaces. Every token is either a positive number consisting of digits 0-9 with no leading zeros, or a word consisting of lowercase English letters.

For example, "a puppy has 2 eyes 4 legs" is a sentence with seven tokens: "2" and "4" are numbers and the other tokens such as "puppy" are words. Given a string s representing a sentence, you need to check if all the numbers in s are strictly increasing from left to right (i.e., other than the last number, each number is strictly smaller than the number on its right in s).

Return true if so, or false otherwise.

Examples

Example 1:

Input: s = "1 box has 3 blue 4 red 6 green and 12 yellow marbles"
Output: true
Explanation: The numbers in s are: 1, 3, 4, 6, 12.
They are strictly increasing from left to right: 1 < 3 < 4 < 6 < 12.

Example 2:

Input: s = "hello world 5 x 5"
Output: false
Explanation: The numbers in s are: 5, 5. They are not strictly increasing.

Example 3:

Input: s = "sunset is at 7 51 pm overnight lows will be in the low 50 and 60 s"
Output: false
Explanation: The numbers in s are: 7, 51, 50, 60. They are not strictly increasing.

Constraints

• 3 <= s.length <= 200
• s consists of lowercase English letters, spaces, and digits from 0 to 9, inclusive.
• The number of tokens in s is between 2 and 100, inclusive.
• The tokens in s are separated by a single space.
• There are at least two numbers in s.
• Each number in s is a positive number less than 100, with no leading zeros.
• s contains no leading or trailing spaces.

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Solution for Strictly Increasing Numbers in Sentence Problem

Intuition and Approach

The problem can be solved using a brute force approach or an optimized approach. The brute force approach directly iterates through the tokens of the sentence, extracts the numbers, and checks if they are strictly increasing. The optimized approach ensures efficient token processing and number validation.

• Brute Force
• Optimized

Approach 1: Brute Force

The brute force approach iterates through each token of the sentence, extracts the numbers, and checks if they are strictly increasing.

Code in Different Languages

C++

Written by @ImmidiSivani

#include <string>
#include <sstream>

class Solution {
public:
    bool areNumbersAscending(std::string s) {
        std::istringstream iss(s);
        std::string token;
        int prevNumber = -1;
        
        while (iss >> token) {
            if (isdigit(token[0])) {
                int number = std::stoi(token);
                if (number <= prevNumber) {
                    return false;
                }
                prevNumber = number;
            }
        }
        
        return true;
    }
};

Java

Written by @ImmidiSivani

class Solution {
    public boolean areNumbersAscending(String s) {
        String[] tokens = s.split(" ");
        int prevNumber = -1;
        
        for (String token : tokens) {
            if (Character.isDigit(token.charAt(0))) {
                int number = Integer.parseInt(token);
                if (number <= prevNumber) {
                    return false;
                }
                prevNumber = number;
            }
        }
        
        return true;
    }
}

Python

Written by @ImmidiSivani

class Solution:
    def are_numbers_ascending(self, s: str) -> bool:
        tokens = s.split()
        prev_number = -1
        
        for token in tokens:
            if token.isdigit():
                number = int(token)
                if number <= prev_number:
                    return False
                prev_number = number
                
        return True

Complexity Analysis

• Time Complexity: $O(n)$
• Space Complexity: $O(n)$
• Where n is the length of the sentence.
• The time complexity is $O(n)$ because we iterate through the tokens once.
• The space complexity is $O(n)$ because we store the tokens in a list.

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Authors:

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