String : Count Words

Question : (Asked to me during a phone interview)

Write a function to count the words in a string. (without using any in-built split functions. The only delimiter is space).

My Thought Process :

Right of the bat , Start counting space characters. But realized that this would fail if all the characters are spaces. Alright, rethink. Make $word_count =0; Start reading characters, if space, skip till next character not a space. Increment the $word_count. But this was also flawed (for input " some word "). So finally after a 2nd rethink. Here's my answer :

public static int word_count(String s1){
// Function to calculate number of words in a string
int count = 0;

if(s1 == null)
return count;

int i= 0 ;
while(i < s1.length()){

while(i <s1.length() && s1.charAt(i) == ' ')
i++;
if(i == s1.length())
break;
else
{
count++;
while(i<s1.length() && s1.charAt(i) != ' ')
i++;
}

}

return count;
}

Complexity :

Time : O(n) : n being number of characters.

Space: O(1) : Just one variable space needed.