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C program to convert roman numbers to decimal numbers
Given below is an algorithm to convert roman numbers to decimal numbers in C language −
Algorithm
Step 1 − Start
Step 2 − Read the roman numeral at runtime
Step 3 − length: = strlen(roman)
Step 4 − for i = 0 to length-1 do
Step 4.1 − switch(roman[i])
Step 4.1.1 − case ‘m’:
Step 4.1.2 − case ‘M’:
Step 4.1.2.1 − d[i]: =1000
Step 4.1.3 − case ‘d’:
Step 4.1.4 − case ‘D’:
Step 4.1.4.1 − d[i]: =500
Step 4.1.5 − case ‘c’:
Step 4.1.6 − case ‘C’:
Step 4.1.6.1 − d[i]: =100
Step 4.1.7 − case ‘l’:
Step 4.1.8 − case ‘L’:
Step 4.1.8.1 − d[i]: =50
Step 4.1.9 − case ‘x’:
Step 4.1.10 − case ‘X’:
Step 4.1.10.1 − d[i]: =10
Step 4.1.11 − case ‘v’:
Step 4.1.12 − case ‘V’:
Step 4.1.12.1 − d[i]: =5
Step 4.1.13 − case ‘i’:
Step 4.1.14 − case ‘I’:
Step 4.1.14.1 − d[i]: =1
Step 5 − for i =0 to length-1 do
Step 5.1 − if (i==length-1) or (d[i]>=d[i+1]) then
Step 5.1.1 − deci += d[i]
Step 5.2 − else
Step 5.2.1 − deci -= d[i]
Step 6 − Print the decimal equivalent of roman numeral
Step 7 − Stop
Program
Following is the C program to convert roman numbers to decimal numbers −
#include <stdio.h>
#include <conio.h>
main(){
char roman[30];
int deci=0;
int length,i,d[30];
printf("The Roman equivalent to decimal
");
printf("Decimal:.........Roman
");
printf("%5d............%3c
",1,'I');
printf("%5d............%3c
",5,'V');
printf("%5d............%3c
",10,'X');
printf("%5d............%3c
",50,'L');
printf("%5d............%3c
",100,'C');
printf("%5d............%3c
",500,'D');
printf("%5d............%3c
",1000,'M');
printf("Enter a Roman numeral:");
scanf("%s",roman);
length=strlen(roman);
for(i=0;i<length;i++){
switch(roman[i]){
case 'm':
case 'M': d[i]=1000; break;
case 'd':
case 'D': d[i]= 500; break;
case 'c':
case 'C': d[i]= 100; break;
case 'l':
case 'L': d[i]= 50; break;
case 'x':
case 'X': d[i]= 10; break;;
case 'v':
case 'V': d[i]= 5; break;
case 'i':
case 'I': d[i]= 1;
}
}
for(i=0;i<length;i++){
if(i==length-1 || d[i]>=d[i+1])
deci += d[i];
else
deci -= d[i];
}
printf("The Decimal equivalent of Roman numeral %s is %d", roman, deci);
}Output
When the above program is executed, it produces the following result −
The Roman equivalent to decimal Decimal:.........Roman 1............ I 5............ V 10............ X 50............ L 100............ C 500............ D 1000............ M Enter a Roman numeral: M The Decimal equivalent of Roman Numeral M is 1000
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