01. Reverse Words in a String III

The problem can be found at the following link: Question Link

My Approach

1. Initialize two variables, start and end, both initially set to 0. These will be used to keep track of the current word boundaries in the string.

2. Enter a while loop that continues until the start pointer reaches the end of the input string s.

3. Inside the outer while loop, enter another while loop that continues until either the end pointer reaches the end of the string or encounters a space character (' ').

4. Inside the inner while loop, the end pointer is incremented until it either reaches the end of the string or finds a space character, effectively identifying the end of the current word.

5. Once the inner while loop completes, it means we have identified a word in the string. At this point, we use the reverse function from the C++ Standard Library to reverse the characters in the identified word. The reverse function takes two iterators, s.begin() + start pointing to the beginning of the word and s.begin() + end pointing to the end of the word, and reverses the characters in that range.

6. After reversing the word, we update the start pointer to end + 1, which sets it to the beginning of the next word (or the character after the space).

7. We also update the end pointer to match the start pointer, effectively resetting it for the next word.

Time and Auxiliary Space Complexity

• Time Complexity: O(n)

• Auxiliary Space Complexity: O(1)

Code (C++)

class Solution {
public:
    string reverseWords(string s) {
        int start=0,end=0;
        while(start<s.length()){
            while(end<s.length() && s[end]!= ' '){
                end++;
            }
            reverse(s.begin()+start,s.begin()+end);
            start=end+1;
            end=start;
        }
        return s;
    }
};

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