COMP2004
Programming Practice
2002 Summer School


Kevin Pulo
School of Information Technologies
University of Sydney

Assignment 1

• Example input/output
• How to find roman numerals
• Worked examples
• Different symbols
• Different number of symbols

Example Input/Output

Input Output
IVXLCDM
34
87
2364
299
4299
44
XXXIV
LXXXVII
MMCCCLXIV
CCXCIX
MMMMCCXCIX
XLIV

• Numbers will always fit into an unsigned long

Example main()

int main() {
std::string symbols;
unsigned long number;
std::cin >> symbols;
while (std::cin >> number) {
std::cout << roman(number,
symbols) << std::endl;
}
}

Symbol values

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1000

First digit

Number Roman
(IVXLCDM) 1 I
2 II
3 III
4 IV
5 V
6 VI
7 VII
8 VIII
9 IX

Second digit

N R N R
(IVXLCDM) 1 I 10 X
2 II 20 XX
3 III 30 XXX
4 IV 40 XL
5 V 50 L
6 VI 60 LX
7 VII 70 LXX
8 VIII 80 LXXX
9 IX 90 XC

Third digit

N R N R
(IVXLCDM) 1 I 100 C
2 II 200 CC
3 III 300 CCC
4 IV 400 CD
5 V 500 D
6 VI 600 DC
7 VII 700 DCC
8 VIII 800 DCCC
9 IX 900 CM

Last digit

N R N R
(IVXLCDM) 1 I 1000 M
2 II 2000 MM
3 III 3000 MMM
4 IV 4000 M?
5 V
6 VI
7 VII
8 VIII
9 IX

Last digit

N R N R
(IVXLCDM) 1 I 1000 M
2 II 2000 MM
3 III 3000 MMM
4 IV 4000 MMMM
5 V 5000 MMMMM
6 VI 6000 MMMMMM
7 VII 7000 MMMMMMM
8 VIII 8000 MMMMMMMM
9 IX 9000 MMMMMMMMM

Worked Example 1

• Input: 2364
• Digits: 2,3,6,4
• Components: 2000,300,60,4
  • 2000: MM
  • 300: XXX
  • 60: LX
  • 4: IV
• Concatenating: MM XXX LX IV
• Without spaces: MMXXXLXIV

Worked Example 2

• Input: 999
• Digits: 9,9,9
• Components: 900,90,9
  • 900: CM
  • 90: XC
  • 9: IX
• Concatenating: CM XC IX
• Without spaces: CMXCIX

Standard Roman symbols

Input Output
IVXLCDM
34
87
2364
299
4299
44
XXXIV
LXXXVII
MMCCCLXIV
CCXCIX
MMMMCCXCIX
XLIV

Different symbols

Input Output
ivxlcdm
34
87
2364
299
4299
44
xxxiv
lxxxvii
mmccclxiv
ccxcix
mmmmccxcix
xliv

Very different symbols

Symbols 34 2940 IVXLCDMXXXIV MMCMXL ivxlcdmxxxiv mmcmxl abcdefgcccab ggegcd 123456733312 775734 !@#$%^*###!@ **%*#$

Different number of symbols

Input 1 Input 2
IVXLC
34
87
2364
299
4299
44
IVXLCDMKP
34
87
2364
299
4299
44

Symbol values IVXLC

Symbol Value
I 1
V 5
X 10
L 50
C 100

Symbol values IVXLCDMKP

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1000
K 5000
P 10000

Number of symbols

• Is always odd and >= 3
• Changes what the "last digit" is

Num IVXLCDM IVXLCDMKP1000 M M4000 MMMM MK5000 MMMMM K9000 9*M MP10000 10*M P100000 100*M 10*P

Assignment requirements

• To get full machine marks, must support:
  • Any set of symbols
  • Any number of symbols
• Partial marks for:
  • Any set of 7 symbols
  • Standard Roman symbols
• Be sure to read the symbols even if you don't use them

3 ways of doing Q2 tute 1b

• Using if-else-if ladder
• Using switch()
• Using an array

if-else-if

#include
#include

int main() {
int month;
std::string s;
if ( ! (std::cin >> month)) {
s = "Invalid number";
} else if (month == 1) {
s = "January";

} else if (month == 2) {
s = "February";
} else if (month == 3) {
s = "March";
} else if (month == 4) {
s = "April";
} else if (month == 5) {
s = "May";
} else if (month == 6) {
s = "June";
} else if (month == 7) {
s = "July";

} else if (month == 8) {
s = "August";
} else if (month == 9) {
s = "September";
} else if (month == 10) {
s = "October";
} else if (month == 11) {
s = "November";
} else if (month == 12) {
s = "December";

} else {
s = "Num out of range";
}
std::cout << s << std::endl;
}

• Very repetitious

switch()

#include
#include

int main() {
int month;
std::string s;
if ( ! (std::cin >> month)) {
s = "Invalid number";
} else {

switch (month) {
case 1:
s = "January";
break;
case 2:
s = "February";
break;
case 3:
s = "March";
break;

case 4:
s = "April";
break;
case 5:
s = "May";
break;
case 6:
s = "June";
break;
case 7:
s = "July";
break;

case 8:
s = "August";
break;
case 9:
s = "September";
break;
case 10:
s = "October";
break;
case 11:
s = "November";
break;

case 12:
s = "December";
break;
default:
s = "Num out ";
s += "of range";
break;
}
}
std::cout << s << std::endl;
}

• Better, but still not great

Array based

#include
#include

std::string months[ ] = { "January",
"February", "March", "April", "May",
"June", "July", "August", "September",
"October", "November", "December" };

int main() {
int month;
std::string s;
if ( ! (std::cin >> month)) {
s = "Invalid number";
} else if (month<1 || month>12) {
s = "Num out of range";
} else {
s = months[month-1];
}
std::cout << s << std::endl;
}




(page 32)