diff_matrix.c

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

#define N 5
#define MAX 10

int f (int m[][N]) {
    int a[N * N], cont = 0, in;
    int i, j, k;

    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            in = 0;
            for (k = 0; k < cont && !in; k++) {
                if (m[i][j] == a[k]) {
                    in = 1;
                }
            }

            if (!in) {
                a[cont] = m[i][j];
                cont++;
            }
        }
    }

    return cont;
}

void print_m(int m[][N]) {
    int i, j;

    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            printf("%d\t", m[i][j]);
        }
        printf("\n");
    }
}

int main (void) {
    int m[N][N], i, j;

    srand(time(0));

    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            m[i][j] = rand() % MAX;
        }
    }

    print_m(m);
    printf("\n\t%d\n", f(m));

    return 0;
}