import CtCILibrary.AssortedMethods;

public class Question {

    // Assume string has sufficient free space at the end

    public static void replaceSpaces(char[] str, int length) {

        int spaceCount = 0, index, i = 0;

        for (i = 0; i < length; i++) {

            if (str[i] == ' ') {

                spaceCount++;

            }

        }

        index = length + spaceCount * 2;

        str[index] = '\0';

        for (i = length - 1; i >= 0; i--) {

            if (str[i] == ' ') {

                str[index - 1] = '0';

                str[index - 2] = '2';

                str[index - 3] = '%';

                index = index - 3;

            } else {

                str[index - 1] = str[i];

                index--;

            }

        }

    }

    public static void main(String[] args) {

        String str = "abc d e f";

        char[] arr = new char[str.length() + 3 * 2 + 1];

        for (int i = 0; i < str.length(); i++) {

            arr[i] = str.charAt(i);

        }

        replaceSpaces(arr, str.length());

        System.out.println("\"" + AssortedMethods.charArrayToString(arr) + "\"");

    }

}