g1901_2000.s2000_reverse_prefix_of_word.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1901_2000.s2000_reverse_prefix_of_word;

// #Easy #String #Two_Pointers #2022_05_09_Time_0_ms_(100.00%)_Space_40.7_MB_(79.75%)

/**
 * 2000 - Reverse Prefix of Word\.
 *
 * Easy
 *
 * Given a **0-indexed** string `word` and a character `ch`, **reverse** the segment of `word` that starts at index `0` and ends at the index of the **first occurrence** of `ch` ( **inclusive** ). If the character `ch` does not exist in `word`, do nothing.
 *
 * *   For example, if `word = "abcdefd"` and `ch = "d"`, then you should **reverse** the segment that starts at `0` and ends at `3` ( **inclusive** ). The resulting string will be `"dcbaefd"`.
 *
 * Return _the resulting string_.
 *
 * **Example 1:**
 *
 * **Input:** word = "abcdefd", ch = "d"
 *
 * **Output:** "dcbaefd"
 *
 * **Explanation:** The first occurrence of "d" is at index 3.
 *
 * Reverse the part of word from 0 to 3 (inclusive), the resulting string is "dcbaefd". 
 *
 * **Example 2:**
 *
 * **Input:** word = "xyxzxe", ch = "z"
 *
 * **Output:** "zxyxxe"
 *
 * **Explanation:** The first and only occurrence of "z" is at index 3.
 *
 * Reverse the part of word from 0 to 3 (inclusive), the resulting string is "zxyxxe". 
 *
 * **Example 3:**
 *
 * **Input:** word = "abcd", ch = "z"
 *
 * **Output:** "abcd"
 *
 * **Explanation:** "z" does not exist in word.
 *
 * You should not do any reverse operation, the resulting string is "abcd". 
 *
 * **Constraints:**
 *
 * *   `1 <= word.length <= 250`
 * *   `word` consists of lowercase English letters.
 * *   `ch` is a lowercase English letter.
**/
public class Solution {
    public String reversePrefix(String word, char ch) {
        int i = 0;
        int j = word.indexOf(ch);
        char[] charArr = word.toCharArray();
        while (i < j) {
            char temp = charArr[i];
            charArr[i] = charArr[j];
            charArr[j] = temp;
            i++;
            j--;
        }
        return String.valueOf(charArr);
    }
}