bidirectional graph structure

main.c

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

#define SIZE 4

/*
 * Gets Row from min(), (diff of x and y) +
 */
int idx(size_t number_nodes, int node1, int node2) {
    int i = (node1 < node2) ? node1 : node2;
    return abs(node1 - node2) + (number_nodes * i) - ((i * (i - 1)) / 2);
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("2 nodes are required\n");
        return 1;
    }

    int node1 = argv[1][0] - 'A';
    int node2 = argv[2][0] - 'A';
    printf("Provided: %c (%d), %c (%d)\n", argv[1][0], node1, argv[2][0], node2);

    if (node1 >= SIZE || node2 >= SIZE || node1 < 0 || node2 < 0) {
        printf("Invalid nodes, must be between 0 and %d\n", SIZE - 1);
        return 1;
    }

    uint32_t *first_array = malloc(sizeof(uint32_t) * SIZE * (SIZE + 1) / 2);
    /*   A  B  C D
     * A 0  1 12 0
     * B 1  0  2 4
     * C 12 2  0 8
     * D 0  4  8 0
     */
    first_array[0] = 0;
    first_array[1] = 1;
    first_array[2] = 12;
    first_array[3] = 0;
    first_array[4] = 0;
    first_array[5] = 2;
    first_array[6] = 4;
    first_array[7] = 0;
    first_array[8] = 8;
    first_array[9] = 0;
    int t1 = idx(SIZE, node1, node2);
    int t2 = idx(SIZE, node2, node1);
    printf("T1: %i\nT2: %i\n", t1, t2);
    printf("V1: %i\nV2: %i\n", first_array[t1], first_array[t2]);
    free(first_array);

    return 0;
}