C and C++ Questions

This is a program to convert a Roman letter to its Decimal Equivalent :

#include

#include

#define maxnumber 10

int value[] = {1000,900,500,400,100,90,50,40,10,9,5,4,1};

char Roman[][3] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};

//CCCLXIX=369

int Find(char key[]) {

int i;

for(i = 12; i>=0; i--) {

if(!strcmp(Roman[i],key)) return value[i];

}

return 0;

}

int Convert(char roman[]) {

int length = strlen(roman) - 1;

int i, val, sum = 0, find;

char tempRoman[4];

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

find = 0;

if(i >= 1) {

tempRoman[0] = roman[i-1];

tempRoman[1] = roman[i];

tempRoman[2] = NULL;

val = Find(tempRoman);

if(val > 0) {

sum += val;

find = 1;

i -= 2;

}

}

if(find == 0) {

tempRoman[0] = roman[i];

tempRoman[1] = NULL;

sum += Find(tempRoman);

i--;

}

}

return sum;

}

int main() {

char roman[100];

// Insert a valid Roman number, all characters must be upper case

// Input range: up to 3999 ( MMMCMXCIX )

while(scanf("%s",roman) != EOF) {

printf("%d\n",Convert(roman));

}

return 0;

}

Basic Knowledge needed to understand this program :

1. U must know C ofcourse .

2. U must Also know how are decimal numbers represented using Roman letters .

How are they represented :

I : This represents 1 and Two I's represent 2 and three I's represent 3 . But this sequence cant be continued for representing four , five etc as it would take more I's . This Gives birth to

v : This represents 5 . placing an I in front of V means 4 . That is IV means 4 . Placing a smaller number in front of larger number indicates Subtraction and placing a smaller number after a larger number indicates Addition . Thus VI means 6[5+1] , VII means 7 , and VIII means 8 .

X : This represents 10 . Hope you found out how to represent 9 . It's IX ,as explainied before subtract I from X . The number of X's indicates the number of tens . Lets take XXIV . As there are 2 X's it indicates 20 and IV is 4. so its 24.

L : L means 50 . Based on what we've learnt so far it should be easy by now to predict how 40 will be represented . ya you are right . Its XL . 10(X) subtracted from 50(L) . And 60,70,80 are LX,LXX,LXXX .

C : C stands for Centum . It means 100 . So by previous explanations XC means 90. CCCLXIX means 369.

D : D stands for 500. Now you will be able to know how to represent 400 . Its simple CD.

M : M means 1000. This is mostly used to represent dates .