Given a string ans a specified character, reverse the prefix that is ended with the specified character.

Intuition

Simulate the process.

Approach

find the first occurrence of the specified character, then reverse the prefix.

Complexity

• Time complexity: find the first occurrence of the specified character. $$O(n)$$

• Space complexity: no extra spaces are needed. $$O(1)$$

Code

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class Solution {
public:
    string reversePrefix(string word, char ch) {
        auto pos = word.find(ch);
        if (pos == word.npos)   return word;
        reverse(word.begin(), word.begin() + pos + 1);
        return word;
    }
};