1-3-URLify.cpp

/*
 * Cracking the coding interview Edition 6
 * Problem 1.3 URLify --> Replace all the spaces in a string with '%20'. 
 * Assumption : We have enough space to accommodate addition chars
 * Preferebly in place
 */

#include <iostream>
#include <cstring>

/*
 * Function : urlify
 * Args     : string long enough to accommodate extra chars + true len 
 * Return   : void (in place transformation of string)
 */

void urlify(char *str, int len)
{
    int numOfSpaces = 0;
    int i = 0, j = 0;
    for ( i = 0; i < len; ++i ) {
        if (str[i] == ' ') {
            ++numOfSpaces;
        }
    }
    
    int extendedLen  = len + 2 * numOfSpaces;
    i = extendedLen - 1;
    for( j = len - 1; j >= 0; --j ) {
        if ( str[j] != ' ' ) {
           str[i--] = str[j];
        } else {
            str[i--] = '0';
            str[i--] = '2';
            str[i--] = '%';
        }
    }
}

int main()
{
    char str[] = "Mr John Smith    ";                       //String with extended length ( true length + 2* spaces)
    std::cout << "Actual string   : " << str << std::endl;
    urlify(str, 13);                                        //Length of "Mr John Smith" = 13
    std::cout << "URLified string : " << str << std::endl;
    return 0;
}