Reverse words in a given string solution in c++

 

Given a String S, reverse the string without reversing its individual words. Words are separated by dots.

Example 1:

Input:
S = i.like.this.program.very.much
Output: much.very.program.this.like.i
Explanation: After reversing the whole
string(not individual words), the input
string becomes
much.very.program.this.like.i

Example 2:

Input:
S = pqr.mno
Output: mno.pqr
Explanation: After reversing the whole
string , the input string becomes
mno.pqr

Your Task:
You dont need to read input or print anything. Complete the function reverseWords() which takes string S as input parameter and returns a string containing the words in reversed order. Each word in the returning string should also be separated by '.' 

Expected Time Complexity: O(|S|)
Expected Auxiliary Space: O(|S|)

Constraints:
1 <= |S| <= 2000

 

solution:

#include<iostream>
#include<stack>
using namespace std;

string reverseWords(string S)
{
	stack<char> s;
	string ans;
	for (int i = S.length()-1; i >= 0; i--)
	{
		if (s.empty())
		{
			s.push(S[i]);
		}
		else if (!(s.empty()))
		{
			if (s.top() == '.')
			{
				s.pop();
				while (!(s.empty()))
				{
					ans += s.top();
					s.pop();
				}
				ans += '.';
			}
			
			s.push(S[i]);
	
		}
	}
	while (s.size())
	{
		ans += s.top();
		s.pop();
	}
	return ans;
}
int main()
{
	string s;
	cout << "Enter string: ";
	cin >> s;

	string result;
	result = reverseWords(s);
	cout << "result: " << result << "\n";

	return 0;
}