Move Spaces to Front of String in Single Traversal

Given a string that has set of words and spaces, our task is to move all spaces to front of string, by traversing the string only once. We will solve this problem quickly in Python using List Comprehension.

Example

Input: string = "python program"
Output: string= “ pythonprogram"

Algorithm

Step1: input a string with word and space.
Step2: Traverse the input string and using list comprehension create a string without any space.
Step 3: Then calculate a number of spaces.
Step 4: Next create a final string with spaces.
Step 5: Then concatenate string having no spaces.
Step 6: Display string.

Example Code

# Function to move spaces to front of string
# in single traversal in Python
def frontstringmove(str):
   noSp = [i for i in str if i!=' ']
   space= len(str) - len(noSp)
   result = ' '*space
   result = '"'+result + ''.join(noSp)+'"
   print ("Final Result ::>",result)
   # Driver program
   if __name__ == "__main__":
      str = input("Enter String")
frontstringmove(str)

Output

Enter String python program
Final Result ::>" pythonprogram"