Breaking a String into Multiple Lines Without Word Splits

Efficiently Splitting Strings by Word Boundaries in TypeScript

Problem

Given a string s and an integer k, break up the string into multiple lines such that each line has a length of k or less. You must break it up so that words don’t break across lines. Each line has to have the maximum possible amount of words. If there’s no way to break the text up, then return null.

You can assume that there are no spaces at the ends of the string and that there is exactly one space between each word.

For example, given the string “the quick brown fox jumps over the lazy dog” and k = 10, you should return: [“the quick”, “brown fox”, “jumps over”, “the lazy”, “dog”]. No string in the list has a length of more than 10.

When working with strings, especially when formatting text, one common problem is ensuring that words do not split across lines. This can be particularly tricky when you have constraints on the maximum length of each line. In this solution, we will explore how to solve this problem efficiently in TypeScript.

Problem Explanation

You are given a string s and an integer k. The task is to break up the string into multiple lines such that:

1. Each line has a length of k or less.
2. Words should not break across lines.
3. Each line should contain the maximum possible number of words.

If it’s impossible to break the string as described, the function should return null.

Example

Given the string "the quick brown fox jumps over the lazy dog" and k = 10, the output should be:

["the quick", "brown fox", "jumps over", "the lazy", "dog"]

Step-by-Step Solution

Step 1: Understand the Constraints

We need to ensure that each line we generate is within the length k, and words should not be split across lines. If a single word exceeds k, it's impossible to split the string as required.

Step 2: Split the String into Words

We will first split the string s into an array of words. This allows us to handle each word individually and decide where to place line breaks.

Step 3: Accumulate Words into Lines

We’ll iterate through the words, adding them to a line until adding another word would exceed k characters. Once a line is full, we'll start a new line.

Step 4: Handle Edge Cases

If any single word exceeds the length k, we'll return null.

TypeScript Implementation

function breakString(s: string, k: number): string[] | null {
    const words = s.split(" ");
    const lines: string[] = [];
    let currentLine = "";

    for (let word of words) {
        // If a word is longer than k, return null
        if (word.length > k) {
            return null;
        }

        // Check if adding the word exceeds the line length
        if (currentLine.length + word.length + (currentLine ? 1 : 0) <= k) {
            currentLine += (currentLine ? " " : "") + word;
        } else {
            // Push the current line to the result and start a new line
            lines.push(currentLine);
            currentLine = word;
        }
    }

    // Add the last line to the result
    if (currentLine) {
        lines.push(currentLine);
    }

    return lines;
}

Explanation

1. Splitting the String: We first split the string s by spaces to get an array of words.
2. Checking Word Length: For each word, if it exceeds the allowed length k, we return null.
3. Building Lines: We attempt to build lines by adding words to the currentLine until it cannot fit more without exceeding the length k. If it does, we save the currentLine and start a new one.
4. Final Step: The last accumulated line is added to the lines array.

Alternative Solutions and Considerations

• Greedy Approach: This approach is greedy, ensuring that each line is filled as much as possible. However, for some special cases, this might not yield the optimal arrangement.
• Dynamic Programming: A more complex solution might involve dynamic programming to find an optimal arrangement of words. However, for most cases, the above greedy approach is efficient and straightforward.

Conclusion

This TypeScript solution efficiently breaks a string into multiple lines, ensuring that no words are split and each line is as full as possible within the given constraints. By carefully handling edge cases, such as words that are too long to fit within the limit, we ensure robustness in the solution.

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