Question

How to select random three consecutive digits from a 6-digit number in C

Answer 1

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

// Function to get random three consecutive digits from a 6-digit number
void getRandomThreeDigits(int num, char *out) {
    char s[16];  // buffer to hold number as string
    sprintf(s, "%06d", num);  // ensure it's 6 digits (pad with zeros if needed)

    if (strlen(s) != 6) {
        strcpy(out, "Err");  // error message
        return;
    }

    int start = rand() % 4;  // Random start index (0–3)
    strncpy(out, s + start, 3);
    out[3] = '\0';  // null-terminate
}

int main(void) {
    srand((unsigned)time(NULL));  // Seed random generator

    int num = 123456;  // Example 6-digit number
    char randomThreeDigits[4];    // buffer for 3 digits + null terminator

    getRandomThreeDigits(num, randomThreeDigits);

    printf("Random three consecutive digits: %s\n", randomThreeDigits);

    return 0;
}

 
  
   
/* 
run:
   
Random three consecutive digits: 234
 
*/

 

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