void replaceBlank(char string[], int length) {
    if (string == nil || length <= 0) {
        return;
    }
    int originalLength = 0;
    int numberBlank = 0;
    int i = 0;
    while (string[i] != '\0') {
        ++originalLength;
        if (string[i] == ' ') {
            ++numberBlank;
        }
        ++i;
    }

    int newLength = originalLength + numberBlank * 2;
    if (newLength > length) {
        return;
    }
    int indexOfOriginal = originalLength;
    int indexOfNew = newLength;
    while (indexOfOriginal >=0 && indexOfNew > indexOfOriginal) {
        NSLog(@"%c", string[indexOfOriginal]);
        NSLog(@"%s", string);
        printf("\n");
        if (string[indexOfOriginal] == ' ') {
            string[indexOfNew--] = '0';
            string[indexOfNew--] = '2';
            string[indexOfNew--] = '%';
        } else {
            string[indexOfNew--] = string[indexOfOriginal];
        }
        --indexOfOriginal;
    }
   NSLog(@"%s", string);
    printf("\n");
}