CareerCup

Yes, possible. Start two pointers i & j from the end of the string.

a. Keep copying the character from ith location to the jth location and decrement both i & j
b. When i encounters a space, decrement i, but not j
c Repeat steps a & b until i falls of the beginning of the string.
d. Keep setting 'space' character at jth location and decrement j unitl j falls of the beginning of the string

It is possible. sites.google.com/site/spaceofjameschen/home/string/move-the-spaces-to-the-starting-of-the-string-in-single-iteration---microsoft

its possible run a iteration from end of the string to the starting.Take two indexes,keep on putting the character at the end except space.Automatically all the spaces will come in front

char str[]=" asdfe sdrfjcz dgrjf ";
int i=0, len=0, count=0;
len = strlen(str);
for(i=len-1; i>=0; i--)
{
if(count ==i)
{
str[i] = ' '; count--;
}
else if(str[i] == ' ')
{
count++; continue;
}
else
{
if(count)
str[i+count] = str[i];
}
}


}

I did in Java, but the technique is very similar. Java code is:

public char[] moveSpaceFront(String data){
        int count = 0;
        char[] str = data.toCharArray();
        int i = str.length - 1;
        while(i >= 0){
            if(str[i] == ' ')
                count++;
            else
                str[i + count] = str[i];
            i--;
        }
        for(i = 0; i < count; i++)
            str[i] = ' ';
        return str;
    }

#include<iostream>
#include<conio.h>
#include<string.h>
using namespace std;

void swap(char str[],int i,int j)
{
      char temp=str[i];
      str[i]=str[j];
      str[j]=temp;
}

int main()
{
    
char str[60];
cout<<"Enter string:";
gets(str);

int len=strlen(str);
int j=len-1;
for(int i=len-1;i>=0;i--)
{
        if(str[i]!='_')
        {                 
                         
                          swap(str,i,j);
                          j--;             
        }        
}

puts(str);
getch();
return 0;    
}

void inlineSpacesMove(char* str, int len, int currLen, int* numSpaces) {
	if (*str == '\0')
		return;
	inlineSpacesMove(str + 1, len, --currLen, numSpaces);
	printf("%s\n", str);

	if ((currLen + (*numSpaces)) == len) {
		*(str) = ' ';
		(*numSpaces)--;
	} else {
		if (*(str - *numSpaces) == ' ')
			(*numSpaces)++;

		if (*numSpaces > 0 && currLen + (*numSpaces) != len) {
			printf("%c \n", *str);
			*str = *(str - (*numSpaces));

		}
	}

}

int main() {
	char *str = malloc(500);

	int numSpaces = 0;
	fgets(str, 500, stdin);
	/* Remove trailing newline, if there. */
	if ((strlen(str) > 0) && (str[strlen(str) - 1] == '\n'))
		str[strlen(str) - 1] = '\0';
	printf("%s ", str);
	inlineSpacesMove(str, strlen(str), strlen(str), &numSpaces);
	printf("%s ", str);
	free(str);
	return 0;
}

I think its possible in one single pass.

public static void Move()
        {
            var input = "ab cd e".ToCharArray();
            Console.WriteLine(input);
            int count = 0;
            for (int i = input.Length - 1; i >= 0; i--)
            {
                if (count != 0 && input[i] != ' ')
                {
                    input[i + count] = input[i];
                }

                if (input[i] == ' ')
                {
                    count++;
                }
            }

            if (count > 0)
            {
                for (int j = 0; j < count; j++)
                {
                    input[j] = ' ';
                }
            }
            Console.WriteLine(input);
        }
    }

#include<stdio.h>
#include<string.h>
int main()
{
char *name = new char(100);
char* name2=new char(100);
int n=0, i=0, spaceC=0, j=0;
strcpy(name, "This is my string");
for(j=i=strlen(name);i>=0;i--,j--){
if(name[i]==' ')
{
i--;
name2[j]=name[i];
name2[spaceC]=' ';
spaceC=spaceC+1;
}
else
name2[j]=name[i];
}
printf("\nthe entered string is '%s'\n", name2);
return 0;

}

#include <stdio.h>
#include <string.h>

main()
{
    char a[500] = " i  s th i   s ev   enpos  si  b      l  e    ";
    printf ("%s\n", a);
    int i;
    int j;
    i = j = strlen(a) - 1;
    while(i)
    {
        if ((a[j] >= 'a' && a[j] <= 'z') && ( --i && --j ))
        ;
        
        else if ( (a[i] == ' ') && --i)
        ;
        
        else if (( a[i] >= 'a' && a[i] <= 'z' ))
        {
            a[j] = a[i];
            a[i] = ' ';
            --i;
            --j;
        }
    }
    printf ("%s\n", a);
    
    return 0;
}

I implemented in java, Its very simple.

public static final char S = '-';
public static String moveSpaceToFirst(String data) {
	char[] values = data.toCharArray();
	int i = values.length-1;
	int c = values.length-1;
	
	while(i>= 0){
		if(values[i] != S) {
			values[c] = values[i];
			if(i!=c) values[i]=S;
			c--;
		}
		i--;
	}
	return new String(values);
}

Implemented in java, its simple.

public static final char S = '-';
public static String moveSpaceToFirst(String data) {
	char[] values = data.toCharArray();
	int i = values.length-1;
	int c = values.length-1;	
	while(i>= 0){
		if(values[i] != S) {
			values[c] = values[i];
			if(i!=c) values[i]=S;
			c--;
		}
		i--;
	}
	return new String(values);
}

void movespacestofront(char* str)
{
    if(str == NULL) return;
	int len = strlen(str);
    int i,j;
	i = j = len-1;
	char space = ' ';
	while(i>=0)
	{
		if(str[i] != space)
		{
			std::swap(str[i--],str[j--]);
		}
		else {
			--i;
		}
	}
}

public static void MoveSpacesToFront(ref char[] input)
        {
            int lastSpace = -1;
            for (int i = input.Length - 1; i >= 0; i--)
            {
                if (input[i] == ' ')
                {
                    lastSpace = Math.Max(lastSpace, i);
                }
                else if (lastSpace != -1)
                {
                    Swap(input, i, lastSpace);
                    lastSpace--;
                }
            }

        }

        private static void Swap(char[] input, int i, int j)
        {
            char temp = input[i];
            input[i] = input[j];
            input[j] = temp;
        }

#include "stdafx.h"
#include <string.h>

int _tmain(int argc, _TCHAR* argv[])
{
//char str[] = {'a',' ','b','c',' ','d'};
char str[] = "H i t h e re! Is t hi s ev en p o s sib le?";
int j=-1;
for(int i= strlen(str) - 1;i>=0;i--)
{
if(str[i] == ' ' && j==-1)
{
j=i;
continue;
}
if(str[i]!=' ' && j!=-1)
{
str[j] = str[i];
str[i] = ' ';
j--;
}
}
printf("%s\n",str);
return 0;
}

void removespaces(string &str)
{
	int t1=0;
	int t2=0;
	while (t2<str.size())
	{
		if(str[t2]==' ')
		{
			t2++;
			continue;
		}
		swap(str[t1],str[t2]);
		t1++;
		t2++;
	}
}

void removespaces(string &str)
{
	int t1=0;
	int t2=0;
	while (t2<str.size())
	{
		if(str[t2]==' ')
		{
			t2++;
			continue;
		}
		swap(str[t1],str[t2]);
		t1++;
		t2++;
	}
}

This is my resolution, and it takes only one iteration.

#include<string>
#include<iostream>
using namespace std;

void moveSpaceToStart(char* pStr) {
	int length = strlen(pStr);
	int count = length - 1;
	int i = length - 1;
	while (i >= 0) {
		if (' ' != pStr[i])
			pStr[count--] = pStr[i];
		i--;
	}
	while (count >= 0) {
		pStr[count--] = ' ';
	}
}

int main(int argc, char* argv[]) {
	char str[] = "this is a test.";
	moveSpaceToStart(str);
	cout << str << endl;
	cin.get();
	return 0;
}

My solution below works well. Not sure if it is qualified for 'one iteration' here as I have a small while loop inside a while loop. However when there are plenty of spaces the small while loop would take trivial time as it marks position to start searching for next non-space character each time.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
char str[]=" Hello I am";

printf("Input: %s\n",str);

char *end = str + strlen(str)-1;
char *next_non_space = NULL;

while(end>=str)
{
if(*end==' ')
{
//Find the next non-space character j from the left substring and move it to end, then set j to space
char *j;
if(next_non_space!=NULL)
{
j = next_non_space;
}
else
{
j = end;
}

while(j>str)
{
j--;
if(*j!= ' ')
{
next_non_space = j; // We found the next non space character at j, next time when we search the 'next' next non space character, we should start from j (j is input but it actually starts at (j-1) in the program)
*end = *j;
*j= ' ';
break;
}
}
}
end--;

}
printf("Output: %s\n",str);

}

My solution below works efficiently. Although I am not sure if it's qualified for 'one iteration' as I have a small while loop inside a while loop. However the small while loop would take trivial time if there are plenty of spaces as it marks the next position to start searching for next non-space character.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
char str[]=" Hello I am";

printf("Input: %s\n",str);

char *end = str + strlen(str)-1;
char *next_non_space = NULL;

while(end>=str)
{
if(*end==' ')
{
//Find the next non-space character j from the left substring and move it to end, then set j to space
char *j;
if(next_non_space!=NULL)
{
j = next_non_space;
}
else
{
j = end;
}

while(j>str)
{
j--;
if(*j!= ' ')
{
next_non_space = j; // We found the next non space character at j, next time when we search the 'next' next non space character, we should start from j (j is input but it actually starts at (j-1) in the program)
*end = *j;
*j= ' ';
break;
}
}
}
end--;

}
printf("Output: %s\n",str);

}

{
i=-1
for j=0,n-1
if c[j]<>' '
++i
swap c[i],c[j]
}

#include <iostream>
using namespace std;

void MoveSpaces(string* line){

string input=*line;
int count=input.length();
int pos1=0,pos2=input.length();
char* charAry=new char[input.length()];
strcpy(charAry,input.c_str());
char* charAry2=new char[input.length()];
string space,non_space;
while(count >= 0){
if(charAry[count] == ' '){
space=charAry[count]+space;
}else{
non_space=charAry[count]+non_space;
}
count--;
}
*line=string(space+non_space);
}
int main(){

string input="H i T h e r e!";
MoveSpaces(&input);
cout << " After function iz : " << input << endl;
}

void moveForward(){
	char A[]="Hello     world how are you";
	char *front=A+ strlen(A)-1;
	char *end=A+ strlen(A)-1;
	
	while(front!=A){
		while(*front!=' '){
			*front--=*end--;
		}
		while(*front ==' '){
			front--;
		}
			
		    *end=*front;
			end--;
			*front=' ';
		
	
	}


	cout << A ;

};

Just use two pointers as explained by Dumbo and replace in the below program '_' with ' '.
'_' is used to see the output clearly.

#include <stdio.h>
void swap(char *s, char *d, int s_c, int d_c){
        char temp = s[s_c];
        s[s_c] = d[d_c];
        d[d_c] = temp;
}

int main()
{
        char string[] = {"__algor__rith_m_"};
        char *s_p, *d_p; /* s_p is space pointer pointing to space */
                        /*d_p is data pointer pointing to any non-space */
        int i, s_p_c, d_p_c;
        /*s_p_c points to the space character which we are working on currently */
        /*d_p_c points to the non-space character which we are working on currently */

        s_p = string;
        d_p = string;
        s_p_c = strlen(string)-1;
        d_p_c = strlen(string)-1;

        while(s_p_c>=0 && d_p_c>=0){
                while(s_p_c >= 0 && s_p[s_p_c] != '_'){
                        s_p_c--;
                }
                if(s_p_c <= 0)
                        goto end;
                d_p_c = s_p_c-1;
                while(d_p[d_p_c] == '_'){
                        d_p_c--;
                }
                if(d_p_c <= 0)
                        goto end;
                swap(s_p, d_p, s_p_c, d_p_c);
                s_p_c--;
                d_p_c--;
        }
end:
        printf("%s\n", string);
}

void movespace(char str[])
{
	int i=0,j=0;
	while(str[i]!='\0')
	{
		if(str[i]!=' ')
		++i;
		else
		{
			swap(str[i],str[j]);
			++j;
		}
	}
	cout<<str;
}

static void Main()
        {
            string inputString = "H  i t h e re! Is t  hi s ev  en p o s sib  le?";
            char[] chars = inputString.ToCharArray();

            for (int i = chars.Length - 1; i > 0; i--)
            {
                while (chars[i] != ' ')
                {
                    i--;
                }
                int j = i;
                while (chars[j] == ' ' && j > 0)
                {
                    j--;
                }

                chars[i] = chars[j];
                chars[j] = ' ';
            }

            foreach (char c in chars)
                Console.Write(c);

            Console.ReadKey();
        }

void moveSpace(char *str)
{
  char *sp_a,*sp_b;
  int bFlag = 0;
  int walker=0;
  int spaceCount = 0;
  char c;
  sp_a = str;
  while(*sp_a)
  {
    sp_a++;
  }
  walker=sp_a-str;
  if (walker <= 1) return ;

  printf("%d",walker);
  --sp_a;

  while(walker--)
  {
    if(*sp_a == ' ')
    {
      if (!spaceCount)
      {
        sp_b = sp_a;
      }
      spaceCount++;
      sp_a--;
      continue;
    }
    if (spaceCount)
    {
       c = *sp_a;
       sp_b[0] = c;
       sp_b--;
    }
    sp_a--;
  }
  sp_a++;
  sp_b++;
  while(sp_a<sp_b)
  {
    *sp_a = ' ';
     sp_a++;
  }
}
int main()
{
  char str[200];
  gets(str);
  moveSpace(str);
  printf("String ------------>%s<----------------",str);

  return 0;
}

This can be done but with recursion.
I hope doing it recursion will count it as one iteration :)
I have used _ in place of space( ) for clarity.
Point me out for any wrong assumptions.

#include "stdio.h"
#include "string.h"

void swap (char *a, char*b)
{
        char t;
        t = *a;
        *a = *b;
        *b = t;
}

void moveSpace (char *str, char **lastSpace)
{
        if (*str == '\0')
        {
                return;
        }

        moveSpace(str+1, lastSpace);
        if (*lastSpace != NULL)
        {
                if (*str != '_')
                {
                        swap (str, *lastSpace);
                        (*lastSpace)--;
                }
        }

        if (*lastSpace == NULL)
        {
                if (*str == '_')
                        *lastSpace = str;
        }
}

void printResult (char *tar, const char *src)
{
        char *last = NULL;
        strcpy (tar, src);
        printf ("Original String: \"%s\"\n", tar);
        moveSpace (tar, &last);
        printf ("New String: \"%s\"\n\n", tar);
}

int main ()
{
        char str[20] = {0};

        printResult (str, "abc_dce__fg__");
        printResult (str, "abc_dce_fg");
}

#include<iostream>

#include<string>
using namespace std;

int main()
{

string str=" this is me, baby^^";
cout<<str<<endl;

int head=0;

for(int i=0; i!=sizeof(str);++i)

{
if (str[i]==' ')
{
for(int j=i;j>0;--j)
{
str[j]=str[j-1];
}
str[head]=' ';
}

}
cout<<str;
return 0;
}