2000_reverse_prefix_of_word.cpp

/*

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.

*/
#include <iostream>
#include <string>


std::string reversePrefix(std::string word, char ch);


int main() {
    std::string str1 = "abcdefd";
    std::string str2;
    char ch = 'd';
    str2 = reversePrefix(str1, ch);
    std::cout << str2 << std::endl;
    return 0;
}

std::string reversePrefix(std::string word, char ch) {
    int len = word.length();
    int idx = -1;
    char temp;
    for (int i = 0; i < len; i++) {
        if (word[i] == ch){
            idx = i;
            break;
        }
    }
    if(idx == -1) return word;

    for (int i = 0; i < idx; i++) {
        temp = word[idx];
        word[idx] = word[i];
        word[i] = temp;
        idx--;

    }
    return word;
}