LC2000.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".
*/


class Solution {
    string reversePrefix(string word, char ch) {
        stack<char> stack;
        string result;

        int index = 0;

        while (index < word.length()) {
            stack.push(word[index]);

            if (word[index] == ch) {
               
               while (!stack.empty()) { 
                 result.push_back(stack.top());
                 stack.pop(); 
                }
                index++;

                while(index < word.length()) {
                    result.push_back(word[index]);
                    index++;
                }
                return result;
            }
        index++;
        }
    return word;
    }
};