Write a program to reverse the given string while preserving the position of spaces.
Examples:
Input : "abc de"
Output : edc ba
Input : "intern at geeks"
Output : skeegt an retni
Input : "Help others"
Output : sreh topleH
- Create a string to store results. Mark the space position of the given string in this string.
- Insert the character from the input string into the result string in reverse order.
- While inserting the character check if the result string already contains a space at index ‘j’ or not. If it contains, we copy the character to the next position.
Below is the implementation of the above steps.
C++
#include <iostream>
using namespace std;
string reverses(string str)
{
int n = str.size();
string result(n, '\0');
for (int i = 0; i < n; i++)
if (str[i] == ' ')
result[i] = ' ';
int j = n - 1;
for (int i = 0; i < str.length(); i++) {
if (str[i] != ' ') {
while(result[j] == ' ')
j--;
result[j] = str[i];
j--;
}
}
return result;
}
int main()
{
string str = "internship at geeks for geeks";
cout << reverses(str) << endl;
return 0;
}
|
Java
public class ReverseStringPreserveSpace {
static void reverses(String str)
{
char[] inputArray = str.toCharArray();
char[] result = new char[inputArray.length];
for (int i = 0; i < inputArray.length; i++) {
if (inputArray[i] == ' ') {
result[i] = ' ';
}
}
int j = result.length - 1;
for (int i = 0; i < inputArray.length; i++) {
if (inputArray[i] != ' ') {
if (result[j] == ' ') {
j--;
}
result[j] = inputArray[i];
j--;
}
}
System.out.println(String.valueOf(result));
}
public static void main(String[] args)
{
reverses("internship at geeks for geeks");
}
}
|
Python3
def reverses(st):
n = len(st)
result = [0] * n
for i in range(n):
if (st[i] == ' '):
result[i] = ' '
j = n - 1
for i in range(len(st)):
if (st[i] != ' '):
if (result[j] == ' '):
j -= 1
result[j] = st[i]
j -= 1
return ''.join(result)
if __name__ == "__main__":
st = "internship at geeks for geeks"
print(reverses(st))
|
C#
using System;
class GFG {
static void reverses(string str)
{
char[] inputArray = str.ToCharArray();
char[] result = new char[inputArray.Length];
for (int i = 0; i < inputArray.Length; i++) {
if (inputArray[i] == ' ') {
result[i] = ' ';
}
}
int j = result.Length - 1;
for (int i = 0; i < inputArray.Length; i++) {
if (inputArray[i] != ' ') {
if (result[j] == ' ') {
j--;
}
result[j] = inputArray[i];
j--;
}
}
for (int i = 0; i < result.Length; i++)
Console.Write(result[i]);
}
public static void Main()
{
reverses("internship at geeks for geeks");
}
}
|
Javascript
<script>
function reverses(str)
{
let inputArray = str.split("");
let result = new Array(inputArray.length);
for (let i = 0; i < inputArray.length; i++) {
if (inputArray[i] == ' ') {
result[i] = ' ';
}
}
let j = result.length - 1;
for (let i = 0; i < inputArray.length; i++) {
if (inputArray[i] != ' ') {
if (result[j] == ' ') {
j--;
}
result[j] = inputArray[i];
j--;
}
}
document.write((result).join(""));
}
reverses("internship at geeks for geeks");
</script>
|
Output:
skeegrofsk ee gtapi hsn retni
Time complexity: O(N)
Auxiliary Space: O(N)
Optimized Solution:
The idea is to use two pointers to reverse.
C++
#include <iostream>
using namespace std;
void preserveSpace(string &str)
{
int n = str.length();
int start = 0;
int end = n - 1;
while (start < end) {
if (str[start] == ' ') {
start++;
continue;
}
else if (str[end] == ' ') {
end--;
continue;
}
else {
swap(str[start], str[end]);
start++;
end--;
}
}
}
int main()
{
string str = "internship at geeks for geeks";
preserveSpace(str);
cout << str;
return 0;
}
|
Java
import java.io.*;
import java.util.*;
class GFG{
public static void preserveSpace(String str)
{
int n = str.length();
int start = 0;
int end = n - 1;
char[] Str = str.toCharArray();
while (start < end)
{
if (Str[start] == ' ')
{
start++;
continue;
}
else if (Str[end] == ' ')
{
end--;
continue;
}
else
{
char temp = Str[start];
Str[start] = Str[end];
Str[end] = temp;
start++;
end--;
}
}
System.out.println(String.valueOf(Str));
}
public static void main(String[] args)
{
String str = "internship at geeks for geeks";
preserveSpace(str);
}
}
|
Python3
def preserveSpace(Str):
n = len(Str)
Str = list(Str)
start = 0
end = n - 1
while(start < end):
if(Str[start] == ' '):
start += 1
continue
elif(Str[end] == ' '):
end -= 1
continue
else:
Str[start], Str[end] = (Str[end],
Str[start])
start += 1
end -= 1
print(''.join(Str))
Str = "internship at geeks for geeks"
preserveSpace(Str);
|
C#
using System;
using System.Collections.Generic;
class GFG{
static void preserveSpace(string str)
{
int n = str.Length;
int start = 0;
int end = n - 1;
char[] Str = str.ToCharArray();
while (start < end)
{
if (Str[start] == ' ')
{
start++;
continue;
}
else if (Str[end] == ' ')
{
end--;
continue;
}
else
{
char temp = Str[start];
Str[start] = Str[end];
Str[end] = temp;
start++;
end--;
}
}
Console.Write(new string(Str));
}
static void Main()
{
string str = "internship at geeks for geeks";
preserveSpace(str);
}
}
|
Javascript
<script>
function preserveSpace(str)
{
let n = str.length;
let start = 0;
let end = n - 1;
let Str = str.split('');
while (start < end)
{
if (Str[start] == ' ')
{
start++;
continue;
}
else if (Str[end] == ' ')
{
end--;
continue;
}
else
{
let temp = Str[start];
Str[start] = Str[end];
Str[end] = temp;
start++;
end--;
}
}
document.write(Str.join(""));
}
let str = "internship at geeks for geeks";
preserveSpace(str);
</script>
|
Output:
skeegrofsk ee gtapi hsn retni
Time complexity: O(n)
Auxiliary Space: O(1)
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