This is my first solution to the snowflake problem given in the book Algorithmic Thinking. I am not a C programmer so read or use with caution.

snowflakes.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <stdbool.h>
const int SIZEOFFLAKESARRAY = 2000;
static int flakes[SIZEOFFLAKESARRAY][6];

void makeSnowflakes() {
    time_t t;
    srand((unsigned) time(&t));
    for (int i = 0; i < SIZEOFFLAKESARRAY; i++) {
        for (int j = 0; j < 6; j++) {
            int num = 1 + rand() % (6);
            flakes[i][j] = num;
        }
    }
}
bool identifyIdentical(int a, int b) {
    bool allSixArmsMatch = true;
    for (int secondArmOffset = 0; secondArmOffset < 6; secondArmOffset++) {
        allSixArmsMatch = true;
        for (int armIndex = 0; armIndex < 6; armIndex++) {
            int totalOffset = armIndex + secondArmOffset;
            if (totalOffset > 5) {
                totalOffset -= 6;
            }
            if (flakes[a][armIndex] != flakes[b][totalOffset]) {
                allSixArmsMatch = false;
                break;
            }
        }
        if (allSixArmsMatch) break;
    }
    if (allSixArmsMatch) printf("\nmatch %d %d \n%d %d %d %d %d %d \n%d %d %d %d %d %d", a, b, 
                       flakes[a][0], flakes[a][1], flakes[a][2], flakes[a][3], flakes[a][4], flakes[a][5], 
                       flakes[b][0], flakes[b][1], flakes[b][2], flakes[b][3], flakes[b][4], flakes[b][5]);
    return allSixArmsMatch;
}
int searchArrayForMatches() {
    bool matched = false;
    int nbrMatched = 0;
    for (int firstSnowflake = 0; firstSnowflake < SIZEOFFLAKESARRAY - 1; firstSnowflake++) {
        for (int secondSnowflake = firstSnowflake + 1; secondSnowflake < SIZEOFFLAKESARRAY; secondSnowflake++) {
            matched = identifyIdentical(firstSnowflake, secondSnowflake);
            if (matched) nbrMatched += 1;
        }
    }
    return nbrMatched;
}
int main() {
    makeSnowflakes();
    
    // create match for test case
    for (int x=0; x<6; x++) {
        int offset = x + 2; if (offset > 5) offset -= 6;
        flakes[SIZEOFFLAKESARRAY - 1][offset] = flakes[SIZEOFFLAKESARRAY - 2][x];
    }
    
    int nbrMatched = searchArrayForMatches();
    printf("\nNumber Matched %d\n", nbrMatched);
    return 0;
}