LeetCode 2000: Reverse Prefix of Word Solution

Master LeetCode problem 2000 (Reverse Prefix of Word), a easy 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.

2000. Reverse Prefix of Word

Easy

Two Pointers String Stack

Problem Explanation

Explanation

To solve this problem, we need to find the index of the first occurrence of the character ch in the given word string. If ch is not found, we do nothing and return the original word. Otherwise, we reverse the segment of word starting from index 0 up to the index of the first occurrence of ch. We can achieve this by using a two-pointer approach where one pointer iterates from the beginning of the string and the other pointer moves until we find the first occurrence of ch. Once we have the index, we reverse the substring using the two pointers.

Start with two pointers start at 0 and end at -1.
Iterate through the word until we find the first occurrence of ch.
Reverse the substring from index 0 to the index of ch.

The time complexity of this solution is O(n) where n is the length of the word string. The space complexity is O(n) for storing the characters of the word string.

Solution Code

class Solution {
    public String reversePrefix(String word, char ch) {
        int end = word.indexOf(ch);
        if (end == -1) {
            return word;
        }
        char[] chars = word.toCharArray();
        int start = 0;
        while (start < end) {
            char temp = chars[start];
            chars[start] = chars[end];
            chars[end] = temp;
            start++;
            end--;
        }
        return new String(chars);
    }
}

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