C++ Program to remove spaces from a string

Given a string, remove all spaces from it. For example “g e e k” should be converted to “geek” and ” g e ” should be converted to “ge”.

The idea is to traverse the string from left to right and ignore spaces while traversing. We need to keep track of two indexes, one for current character being red and other for current index in output.

// C++ program to evaluate a given expression 
#include <iostream> 
using namespace std; 
  
char *removeSpaces(char *str) 
{ 
    int i = 0, j = 0; 
    while (str[i]) 
    { 
        if (str[i] != ' ') 
           str[j++] = str[i]; 
        i++; 
    } 
    str[j] = '\0'; 
    return str; 
} 
  
// Driver program to test above function 
int main() 
{ 
    char str1[] = "gee    k   "; 
    cout << removeSpaces(str1) << endl; 
  
    char str2[] = " g e e k "; 
    cout << removeSpaces(str2); 
    return 0; 
}

Output:

geek
geek

Time complexity of above implementation is O(n) where n is number of characters in input string.

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