How to convert DDMMAYY to DD/MM/YYYY in C

Question

#include <stdio.h>
// tetando ex 01 

int main(){
 int dia,mes,ano, data;
  printf("Digite a data em DDMMAAA: ");
  scanf("%d", &data );
  
  dia= data/1000000;
  printf("%d", dia);
 
  
}

I can’t develop the logic to separate month and year from the DDMMAAA format someone can give me some hint, I also searched in the machine to understand if there was any formula but I’m not getting.

Answer 1

You can do it using only math:

#include <stdio.h>

int main() {
    int data;
    printf("Digite a data em DDMMAAAA: ");
    scanf("%d", &data);
  
    int dia = (data / 1000000) % 100;
    int mes = (data / 10000) % 100;
    int ano = data % 10000;
    printf("A data em DD/MM/AAAA é %02d/%02d/%04d.\n", dia, mes, ano);
}

Read

• data divided by 10ª as "return data without the last n digits"; and

• data module 10Šo as "return data only with the last n digits".

Assuming the value entered by the user was 01082021, in the case of mes, for example: when I do 01082021 / 10000, I say remove the last four digits of 01082021, getting 0108. Then when do I 0108 % 100, I say keep the last two digits of 0108, getting 08, which is the month of the date inserted.

---

Or, how @user140828 noticed but did not detail, store in a char[9]:

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

int main() {
    char data[9];
    printf("Digite a data em DDMMAAAA: ");
    scanf("%s", data);
    
    char dia[3]; strncpy(dia, data, 2); dia[2] = '\0';
    char mes[3]; strncpy(mes, data + 2, 2); mes[2] = '\0';
    char ano[5]; strncpy(ano, data + 4, 4); ano[4] = '\0';
    printf("A data em DD/MM/AAAA é %s/%s/%s.\n", dia, mes, ano);
}

However, the day, month and year will be as strings. If you want to turn them into integers to manipulate them later, use the function atoi:

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

int main() {
    char data[9];
    printf("Digite a data em DDMMAAAA: ");
    scanf("%s", data);
    
    char diaStr[3]; strncpy(diaStr, data, 2); diaStr[2] = '\0';
    char mesStr[3]; strncpy(mesStr, data + 2, 2); mesStr[2] = '\0';
    char anoStr[5]; strncpy(anoStr, data + 4, 4); anoStr[4] = '\0';
    
    int dia = atoi(diaStr);
    int mes = atoi(mesStr);
    int ano = atoi(anoStr);
    printf("A data em DD/MM/AAAA é %02d/%02d/%04d.\n", dia, mes, ano);
}