CareerCup

Take a chasing pointers approach - keep a current pointer to mark position in the array, and a tail pointer such that the start of array to tail is free of commas.

char[] arr = "1,234,34,54";  

char *RemoveCommas(char *arr) { 
	char *curr = arr, *tail = arr; 
         while (*curr) { 
             if (*curr != ',') {
                  if (curr != tail) 
                       *tail = *curr;
                 curr++;
                 tail++;
            } else  
                curr++;     
         }
         *tail = '\0';
         return arr;
}

Yet another C approach (fully runnable).

This is pretty simple, but note the check for (t < s) may be more wasteful than simply overwriting *t with its own value. There's no harm in that, and you would avoid a conditional.

#include <stdio.h>

void remove_commas(char *s) {
    char *t;
    char c;

    for (t = s; c = *s; ++s) {
        if (c == ',') continue;
        if (t < s) *t = c;
        ++t;
    }
    *t = '\0';
}

int main(int argc, char **argv) {
    char arr[] = "1,234,34,54";
    remove_commas(arr);
    printf("%s\n", arr);
    return 0;
}

Java:

public static void remove(char[] data) {
	int offset=0;
	for (int i=0; i<data.length; i++)
		if (data[i]==',')
			offset++;
		else
			data[i-offset]=data[i];
}

one liner in Python

arr = "1,234,34,54"
print arr.replace(',','')

C++ Strings

#include <iostream>
using namespace std;
int main() {
    string s = "1,204,342,544";
    s.erase(remove(s.begin(), s.end(), ',' ), s.end());
    cout << s;
}

char arr[] = "1,234,56,7,8,9,11,12";
   char *c = arr;
   char *n = NULL;

   while( *c != '\0') {

       if ( ( *c == ',' ) && ( !n ) ) {
            n = c;
       } else if ( ( *c == ',' ) && n ) {
       } else if ( n ) {
            *n = *c;
            n++;
       }

       c++;
   }

   if ( n ) { *n = '\0'; }

in C:

char array[] = "2,234,1,345";
int j =0;
for(int i = 0; i<strlen(array); i++)
{
if(array[i] != ',')
array[j++] = array[i];
}
array[j] = '\0';

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

void main(){
char s[] = "1,234,34,54";
int len=strlen(s);
int i=0;
while( *s != '\0') {
	i++;
	if (*s==',') memmove(s,s+1,len-i);
	s++;
}
}

char* remove_comma(char* str)
{ 
      int n = strlen(str), i(0),  k(0);
     while (i < n)
     {
             if (str[i] == ',') i++;
             else str[k++] = str[i++];
     }
     str[k] = '\0';
     return str;
}

public class removeComma {
	public static void main(String args[]){
		String arr = "1,234,34,54";
		StringBuffer a = new StringBuffer();
		for(int i =0;i<arr.length();i++)
		if(arr.charAt(i) != ',')
			a.append(arr.charAt(i));
		System.out.println(a.toString());		
	}
}

You will be shifting everything left. Use pointers s, d and copy s into d. Then if s == ',' increase s so that you copy some number into d.

int main() {
    char str[20] = "123,45,6,7,9";
    int d = 0,  s = 0;
    while (str[s] != '\0') if (str[s] == ',') s++; else str[d++] = str[s++];
    while (str[d] != '\0') str[d++] = ' ';
    cout << str << endl;
}

As we go through the string, keep count of comma and use that counter to pick the element to be overwritten.

int _tmain(int argc, _TCHAR* argv[])
{
char array[] = {"1,234,34,54"};
int iLen = strlen(array);
int comma_count = 0;
int i = 0;
while( i < iLen)
{
if(array[i] == ',')
comma_count++;
else
array[i-comma_count] = array[i];
i++;
}
array[iLen-comma_count] = 0;
}

public static void main(String[] args) {
		// TODO Auto-generated method stub
		String arr = "1,234,34,54";
		
		StringBuilder input = new StringBuilder(arr);
		
		for(int i = 0; i<input.length(); i++){
			
			if(input.charAt(i) == ','){
				
				input.deleteCharAt(i);
			}
				
		}
		
		System.out.println(input.toString());

	}

Here is an Iterative version:

...
	char szText[]="1,234,34,54";
	cout << "Source    text: " << szText << endl;
	size_t iLen = strlen( szText );
	size_t iPos = 0;
	char *pszText = szText;
	while( iPos < iLen )
	{
		if( *pszText++ != ',' )
			iPos++;
		else
		{
			strcpy( &szText[iPos], pszText );
			pszText = &szText[iPos];
			iLen--;
		}
	}
	cout << "Corrected text: " << szText << endl;
...

Output:
Source text: 1,234,34,54
Corrected text: 12343454

public char[] removeCommas(char[] a)
    {
    	int count=0,n=a.length;
    	for(int i=0;i<a.length;i++)
    	{
    		if(a[i] == ',')
    		{
    			count++;
    		}
    		else
    		   a[i-count]=a[i];
    	}
    	
    	if(count > 0)
        	a[n-count]='\0';
    	return a;

}

int main()
{
char s[] = "1234,34,54";
char *p = s-1;
char *q = s + strlen(s);
char *r = NULL;

while (++p < q) {
if (*p == ',') {
r = p;
break;
}
}

if (r != NULL) {
while (++p < q) {
if (*p != ',') {
*r++ = *p;
}
}
*r = '\0';
}
std::cout << s << endl;
return 0;
}

void main()
{
	char arr[] = "1,234,34,54";
	int count = 0;
	int len = strlen(arr);
	char *c = new char[len];
	for(int i=0;i<len;i++)
		c[i] = '\0';
	for(int i =0 ;i<len;i++)
		if(arr[i] != ',')
		{
			c[count] = arr[i];
			count++;
		}
	cout<<c;
}