Here you will get program to convert decimal number to roman numeral in C and C++.

**How it Works?**

- Divide the given number in the order 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 to find largest base value.
- Display the corresponding roman symbol of largest base value obtained by above method in output.
- Subtract the given number with largest base value to get new number.
- Repeat above process with the new number until it becomes 0.

**Example:**

Decimal Number: 250

- Divide it in order 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 to find largest base value. Here 250 is divided by 100. The corresponding roman symbol for 100 is C.
- Subtract 250 with 100 (largest base value in previous step) to get new number i.e. 150.
- Again divide 150 in the order mentioned earlier. It is divided by 100, so corresponding roman symbol is C.
- Subtract 150 with 100 to get new number i.e. 50.
- Divide 50 again in the order mentioned earlier. 50 is divided by 50, so corresponding roman symbol is L.
- Subtract 50 with 50. The new number obtained is 0 so we stop here.
- The final roman numeral is
**CCL**.

Below program implements above algorithm.

## Program to Convert Decimal Number to Roman Numeral in C

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#include<stdio.h> void decimal2roman(int num){ int decimal[] = {1000,900,500,400,100,90,50,40,10,9,5,4,1}; //base values char *symbol[] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"}; //roman symbols int i = 0; while(num){ //repeat process until num is not 0 while(num/decimal[i]){ //first base value that divides num is largest base value printf("%s",symbol[i]); //print roman symbol equivalent to largest base value num -= decimal[i]; //subtract largest base value from num } i++; //move to next base value to divide num } } int main() { printf("250 -> "); decimal2roman(250); printf("\n1550 -> "); decimal2roman(1550); printf("\n670 -> "); decimal2roman(670); return 0; } |

**Output**

*250 -> CCL*

*1550 -> MDL*

*670 -> DCLXX*

## Program to Convert Decimal Number to Roman Numeral in C++

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#include<iostream> using namespace std; void decimal2roman(int num){ int decimal[] = {1000,900,500,400,100,90,50,40,10,9,5,4,1}; //base values char *symbol[] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"}; //roman symbols int i = 0; while(num){ //repeat process until num is not 0 while(num/decimal[i]){ //first base value that divides num is largest base value cout<<symbol[i]; //print roman symbol equivalent to largest base value num -= decimal[i]; //subtract largest base value from num } i++; //move to next base value to divide num } } int main() { cout<<"250 -> "; decimal2roman(250); cout<<"\n1550 -> "; decimal2roman(1550); cout<<"\n670 -> "; decimal2roman(670); return 0; } |

Comment below if you any queries related to above program.

sir,how can i write the programs without any time complexity and space complexity

this programm is generating error. Value of type void is not allowed.

It’s wrong. 999 returns CMXCIX, instead of IM.

The decimal to Roman code doesn’t work properly. It works only for additive cases (i.e. where the Roman symbols all add to each other, like XVI = 36), not for subtractive cases (where the digit on the left gets subtracted), e.g. XIV = 34.