LeetCode 758: Bold Words in String Solution

Master LeetCode problem 758 (Bold Words in String), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

758. Bold Words in String

Medium

Array Hash Table String Trie String Matching

Problem Explanation

Explanation:

Given a string s and a list of strings words, we need to bold all occurrences of the words in s. A word is bold if it appears in s and all letters in the word are bolded. The objective is to return the final bolded string.

To solve this problem, we can iterate through all substrings of s and check if each substring matches any word in words. If a match is found, we mark the corresponding characters in s as bold. To mark the characters as bold, we maintain a boolean array bold of the same length as s, where bold[i] is true if the character at index i in s is bold, and false otherwise.

The steps to solve the problem are as follows:

Initialize the bold array with false for each character in s.
Iterate through all substrings of s and check if each substring matches any word in words.
If a match is found, update the bold array to mark the characters as bold.
Construct the final bolded string using the bold array.

The time complexity of this approach is O(nml), where n is the length of the input string s, m is the number of words in the input list words, and l is the average length of words in words. The space complexity is O(n) to store the bold array.

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Solution Code

class Solution {
    public String boldWords(String[] words, String s) {
        boolean[] bold = new boolean[s.length()];
        for (String word : words) {
            int index = s.indexOf(word, 0);
            while (index != -1) {
                for (int i = index; i < index + word.length(); i++) {
                    bold[i] = true;
                }
                index = s.indexOf(word, index + 1);
            }
        }
        
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            if (bold[i] && (i == 0 || !bold[i - 1])) {
                sb.append("<b>");
            }
            sb.append(s.charAt(i));
            if (bold[i] && (i == s.length() - 1 || !bold[i + 1])) {
                sb.append("</b>");
            }
        }
        
        return sb.toString();
    }
}

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