557. Reverse Words in a String III

2020, Dec 05 One min read

1. Description

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

2. Example

Example 1

Input: “Let’s take LeetCode contest”
Output: “s’teL ekat edoCteeL tsetnoc”

3. Note

In the string, each word is separated by single space and there will not be any extra space in the string.

4. Solutions

String

n = i_record.size()
Time complexity: O(n)
Space complexity: O(1)

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class Solution
{
public:
    // string reverseWords(string s)
    string reverseWords(string &m_sentence)
    {
        int wordBeginIndex = 0;
        for(int i = 0; i < m_sentence.size(); i++)
        {
            if(m_sentence[i] == ' ')
            {
                reverse(m_sentence.begin() + wordBeginIndex, m_sentence.begin() + i);

                wordBeginIndex = i + 1;
                // it will not reach m_sentence.size(), since the char before belongs to a word rather than blank
            }
        }

        reverse(m_sentence.begin() + wordBeginIndex, m_sentence.end());

        return m_sentence;
    }
};

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