Reverse a String

Write a simple code to reverse a string.

INPUT: "HELLO WORLD"
OUTPUT: "DLROW OLLEH"

The logic to reverse a string is simple, swap the first character with last character, the second character with the second-last character and so on...

Take two variables low and high to hold the indices of first and last element, increment low and decrement high as long as low<high.

CODE:

void reverse(char* str, int n) 
{   
   if(str == NULL || n <= 1)     
      return;      
   int low = 0;   
   int high = n-1;      

   while(low < high)   
   {     
      char temp = str[low];       
      str[low] = str[high];       
      str[high] = temp;       
      low++;       
      high--;     
   }   
}  

The code traverse the string only once and takes O(n) time.