Program that converts roman numerals to numbers in C language

i am trying to make program for roman numbers converter. in C language
But we have some rules.

Letters are written from left to right and from largest to smallest value.
Example u want to write 1907.But we cant use same letter 4 times.and for the value 900 we should think of it as 1000-100.its write like that CM Not like MC.

and some examples

my most important problem is how ı can change string letter to value

thank u

my example with description

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

void main() {

/*
Roma Rakamları Ve Değerleri

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

*/

/*
Soru 1-
MCMVII
MMXI
XC
MCMXC

değerlei sırasi ile kaçtır

*/
int I = 1;
int V = 5;
int X = 10;
int L = 50;
int C = 100;
int D = 500;
int M = 1000;

char que1[] = "MCMVII";
char que2[] = "MMXI";
char que3[] = "XC";
char que4[] = "MCMXC";

for (int i = 0; i < strlen(que1)-1; i++)
{
    if (que1[i]>que1[i+1])
    {
        printf("%c",que1[i]);
        //Then I will collect the letters one by one myself.
    }else if (que1[i]<que1[i+1])
    {
        printf("%c",que1[i+1]);
        i++;
        //i skipped (i+1).letter
    } 
}






}

>Solution :

• You need to keep track of the previous value (i.e., prev).
• If the current value was bigger than previous value, subtract it from the result twice so that we wouldn’t count it twice.

Code

#include <stdio.h>
#include <string.h>

int romanToInt(char *s) {
  int vals[26];
  vals['I' - 'A'] = 1;
  vals['V' - 'A'] = 5;
  vals['X' - 'A'] = 10;
  vals['L' - 'A'] = 50;
  vals['C' - 'A'] = 100;
  vals['D' - 'A'] = 500;
  vals['M' - 'A'] = 1000;

  int res = 0;
  int prev = 0;

  for (int i = 0; s[i] != '\0'; i++) {
    int curr = vals[s[i] - 'A'];
    res += curr;
    if (curr > prev) {
      res -= 2 * prev;
    }
    prev = curr;
  }

  return res;
}

int main() {
  char que1[] = "MCMVII";
  char que2[] = "MMXI";
  char que3[] = "XC";
  char que4[] = "MCMXC";

  printf("%s: %d\n", que1, romanToInt(que1));
  printf("%s: %d\n", que2, romanToInt(que2));
  printf("%s: %d\n", que3, romanToInt(que3));
  printf("%s: %d\n", que4, romanToInt(que4));
}

Prints

MCMVII: 1907
MMXI: 2011
XC: 90
MCMXC: 1990