Given a string that has set of words and spaces, write a program to move all spaces to front of string, by traversing the string only once.
Examples:
Input : str = "geeks for geeks" Output : ste = " geeksforgeeks" Input : str = "move these spaces to beginning" Output : str = " movethesespacestobeginning" There were four space characters in input, all of them should be shifted in front.
Method 1 (Using Swap)
Idea is to maintain two indices i and j. Traverse from end to beginning. If the current index contains space, swap chars in index i with index j. This will bring all spaces to beginning of the array.
C++
// CPP program to bring all spaces in front of // string using swapping technique #include<bits/stdc++.h> using namespace std; // Function to find spaces and move to beginning void moveSpaceInFront(char str[]) { // Traverse from end and swap spaces int i = strlen(str)-1; for (int j = i; j >= 0; j--) if (str[j] != ' ') swap(str[i--], str[j]); } // Driver code int main() { char str[] = "Hey there, it's GeeksforGeeks"; moveSpaceInFront(str); cout << str; return 0; } |
Java
// Java program to bring all spaces in front of // string using swapping technique class GFG { // Function to find spaces and move to beginning static void moveSpaceInFront(char str[]) { // Traverse from end and swap spaces int i = str.length-1; for (int j = i; j >= 0; j--) if (str[j] != ' ') { char c = str[i]; str[i] = str[j]; str[j] = c; i--; } } // Driver code public static void main(String[] args) { char str[] = "Hey there, it's GeeksforGeeks".toCharArray(); moveSpaceInFront(str); System.out.println(String.valueOf(str)); } } // This code is contributed by // 29AjayKumar |
Python3
# Python3 program to bring all spaces # in front of string using swapping technique # Function to find spaces and move to beginning def moveSpaceInFront(s): # Traverse from end and swap spaces i = len(s) - 1; for j in range(i, -1, -1): if (s[j] != ' '): s = swap(s, i, j); i -= 1; return s; def swap(c, i, j): c = list(c) c[i], c[j] = c[j], c[i] return ''.join(c) # Driver code s = "Hey there, it's GeeksforGeeks"; s = moveSpaceInFront(s); print(s); # This code is contributed # by Princi Singh |
C#
// C# program to bring all spaces in front of // string using swapping technique using System; class GFG { // Function to find spaces and move to beginning static void moveSpaceInFront(char []str) { // Traverse from end and swap spaces int i = str.Length-1; for (int j = i; j >= 0; j--) if (str[j] != ' ') { char c = str[i]; str[i] = str[j]; str[j] = c; i--; } } // Driver code public static void Main() { char []str = "Hey there, it's GeeksforGeeks".ToCharArray(); moveSpaceInFront(str); Console.WriteLine(String.Join("",str)); } } // This code is contributed by PrinciRaj1992 |
Output:
Heythere,it'sGeeksforGeeks
Time complexity-: O(n)
Auxiliary Space-: O(1)
Method 2 (Without using swap)
The idea is to copy all non-space characters to end. Finally copy spaces.
C++
// CPP program to bring all spaces in front of // string using swapping technique #include<bits/stdc++.h> using namespace std; // Function to find spaces and move to beginning void moveSpaceInFront(char str[]) { // Keep copying non-space characters int i = strlen(str); for (int j=i; j >= 0; j--) if (str[j] != ' ') str[i--] = str[j]; // Move spaces to be beginning while (i >= 0) str[i--] = ' '; } // Driver code int main() { char str[] = "Hey there, it's GeeksforGeeks"; moveSpaceInFront(str); cout << str; return 0; } |
Java
// Java program to bring all spaces in front of // string using swapping technique class GFG { // Function to find spaces and move to beginning static void moveSpaceInFront(char str[]) { // Keep copying non-space characters int i = str.length-1; for (int j = i; j >= 0; j--) if (str[j] != ' ') str[i--] = str[j]; // Move spaces to be beginning while (i >= 0) str[i--] = ' '; } // Driver code public static void main(String[] args) { char str[] = "Hey there, it's GeeksforGeeks".toCharArray(); moveSpaceInFront(str); System.out.println(String.valueOf(str)); } } // This code is contributed by Rajput-Ji |
Python3
# Python3 program to bring all spaces # in front of sing using swapping technique # Function to find spaces and # move to beginning def moveSpaceInFront(s): # Keep copying non-space characters i = len(s) - 1; for j in range(i, -1, -1): if (s[j] != ' '): s = s[:i] + s[j] + s[i + 1:] i -= 1; # Move spaces to be beginning while (i >= 0): s = s[:i] + ' ' + s[i + 1:] i -= 1 return s; # Driver code s = "Hey there, it's GeeksforGeeks"; s = moveSpaceInFront(s); print(s); # This code is contributed # by Princi Singh |
C#
// C# program to bring all spaces in front of // string using swapping technique using System; class GFG { // Function to find spaces and move to beginning static void moveSpaceInFront(char []str) { // Keep copying non-space characters int i = str.Length-1; for (int j = i; j >= 0; j--) if (str[j] != ' ') str[i--] = str[j]; // Move spaces to be beginning while (i >= 0) str[i--] = ' '; } // Driver code public static void Main(String[] args) { char []str = "Hey there, it's GeeksforGeeks". ToCharArray(); moveSpaceInFront(str); Console.WriteLine(String.Join("",str)); } } // This code is contributed by Rajput-Ji |
Output:
Heythere,it'sGeeksforGeeks
Time complexity-: O(n)
Auxiliary Space -:O(1)
This article is contributed by SAKSHI TIWARI. If you like GeeksforGeeks(We know you do!) and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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