Matrix manipulation to find biggest elements in their row & column - arrays

Question

Our teacher asks to manipulate and search through a 25x15 matrix to find the biggest elements in their own Row & Column: if the (i,j) element is bigger than the mean value of i row, and bigger than the mean value of j column, then we can increment the counter that we'll return from the given function. After we found all of these so-called "Important Points" we search in them for the biggest of all, and pass the value and its coordinates to the Main by using the pointers passed to the function to modify the original variables.
The core of the exercise is the function to implement, with the given arguments:
int Importants(int a[ROW][COL], int *mi, int *mj, int *max);
I preferred to use more little functions to call when needed, than to implement everything in a big block, so I created the functions to find the mean value of a given column and row, the biggest element in a row.
We tried to use a supplementary array to store the positions, to bypass the pointers requisite, which contains a triplet of (i,j coordinate + value); anyway I'm not sure it's the right way.
Here's the full source-code
/*
In a matrix, the (i,j) couple is considered "IMPORTANT" is its value is
Bigger Than the Mean Value of the i row && Bigger Than the Mean Value of the j column
The exercise is to create, aside from Create (in the given interval) and Print functions, a function
named "Importants" which returns the number of Important points of the matrix; then search in these points
which one is the biggest and returns its value and coordinates by using the pointers defined in the function call.
FUNCTION DEFINITION CAN NOT BE ALTERED
*/
//import libraries
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
//constant defines
#define ROW 25
#define COL 15
#define MIN 3
#define MAX 47
//vector with (i,j) positions and their value: every 3 elements you have 'i' row number, 'j' column number, and 'k' or 'max' value
int positions[COL*3];
//matrix generation with no first row element equal to the previous and next one
void create_matrix(int mat[][COL]) {
for (int i = 0; i < ROW; i++) {
for (int j = 0; j < COL; j++) {
//first generation try
mat[i][j] = rand() % (MAX - MIN + 1) + MIN;
//checks
if ((mat[i][j] == mat[i-1][j]) && (mat[i][j] == mat[i+1][j]) && (i >= 1)) {
if (j > 0){
j--;
continue;
}
else {
continue;
}
}
else if ((mat[i][j] == mat[i+1][j]) && i >= 1) {
if (j > 0){
j--;
}
else {
continue;
}
}
}
}
puts("Matrix Generated.\n\n");
}
//generate a vector with all zeros to avoid mistakes
void zero_vector(int vector[]) {
for (int i = 0; i < COL*3;i++) {
vector[i] = 0;
}
}
//print matrix
void print_matrix(int mat[][COL]) {
for (int i = 0; i < ROW; i++) {
for (int j = 0; j < COL; j++) {
printf("[ %2i ] ", mat[i][j]);
}
printf("\n");
}
}
//find max element in a given row
int max_in_row(int mat[][COL], int i) {
int max_value = 0, second_max = 0;
for (int r = i, c = 0; c < COL; c++) {
if (mat[r][c] > max_value) {
second_max = max_value;
max_value = mat[r][c];
}
}
return max_value;
}
//find max element in Positions vector
void max_in_positions_vector(int vector[]) {
int max_value = 0, second_max_value = 0;
for (int i = 2; i < COL*3; i=i+3) {
if (vector[i] > max_value) {
second_max_value = max_value;
max_value = vector[i];
}
}
printf("\n\nThe biggest of \'Important Positions\' is:\t%i", max_value);
}
//calculate mean value of a given row
int row_mean_value(int mat[][COL], int i, int j) {
int r_mean = 0, sum = 0;
for (int r = i, c = j; c < COL; c++){
sum += mat[r][c];
}
r_mean = sum / COL;
printf("\nMean value of Row %i:\t%i", i, r_mean);
return r_mean;
}
//calculate mean value of a given column
int column_mean_value(int mat[][COL], int i, int j) {
int c_mean = 0, sum = 0;
for (int r = i, c = j; r < ROW; r++){
sum += mat[r][c];
}
c_mean = sum / ROW;
printf("\nmedia colonna %i:\t%i", i, c_mean);
return c_mean;
}
int Importants(int a[ROW][COL], int *mi, int *mj, int *max){
int i = 0, j = 0, n_Importants = 0, max_value, k;
for (i,k = 0; i < ROW; i++) {
max_value = max_in_row(a, i);
//row_mean_value(a,i,j);
for (j = 0; j < COL; j++) {
if (max_value > row_mean_value(a,i,j) && max_value > column_mean_value(a,i,j)){
n_Importants++;
positions[k] = i;
positions[k+1] = j;
positions[k+2] = max_value;
k += 3;
//debug prints
printf("\nMax Value n. %i:\t%i", j, max_value);
printf("\ni = %i\tj = %i\tk = %i\n\n", i, j, k);
}
}
}
return n_Importants;
}
//main function
int main() {
srand(time(NULL));
int mat[ROW][COL];
int mi = 0, mj = 0, max = 0, *mi_p = &mi, *mj_p = &mj, *max_p = &max;
create_matrix(mat);
print_matrix(mat);
zero_vector(positions);
int n_Importants = Importants(mat, mi_p, mj_p, max_p);
max_in_positions_vector(positions);
return 0;
}
I've updated the k cycle to iterate every k+3 as suggested only inside the if block; As noted, mi, mj are not used, and that's part of the problem and why I chose to use an array of positions: the "Importants" function definition can not be altered, and so I would have to use the variable pointers. Also I've edited the call to the max_in_vector function to the correct max_in_row function name.

Answer 1

Updates
I've worked on it, removed the positions array and used the pointers to pass back the coordinates, by implementing a search in the matrix from within the Importants function; I've adjusted the search because I think I have to check every element, else it would only check for the maximum of the row && column. I don't know how to explain it well, so I'll post the updated code:
//imports
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
//global constants
#define ROW 25
#define COL 15
#define MIN 3
#define MAX 47
//int posizioni[COL*3];
int importants_vect[ROW*COL];
//create matrix with no duplicates for the first element of 2 adjacent rows (a[i][j] != a[i-1][j] AND a[i][j] != a[i+1][j])
void create_matrix(int mat[][COL]) {
for (int i = 0; i < ROW; i++) {
for (int j = 0; j < COL; j++) {
mat[i][j] = rand() % (MAX - MIN + 1) + MIN;
if ((mat[i][j] == mat[i-1][j]) && (mat[i][j] == mat[i+1][j]) && (i >= 1)) {
if (j > 0){
j--;
continue;
}
else {
continue;
}
}
else if ((mat[i][j] == mat[i+1][j]) && i >= 1) {
if (j > 0){
j--;
}
else {
continue;
}
}
}
}
puts("Matrix Generated.\n\n");
}
void zero_vector_init(int vect[]) {
for (int i = 0; i < COL*3;i++) {
vect[i] = 0;
}
}
//print matrix function
void print_matrix(int mat[][COL]) {
for (int i = 0; i < ROW; i++) {
for (int j = 0; j < COL; j++) {
printf("[ %2i ] ", mat[i][j]);
}
printf("\n");
}
}
/* void maxi_vect(int vect[]) {
int max_value = 0, second_max_value = 0;
for (int i = 2; i < COL*3; i=i+3) {
if (vect[i] > max_value) {
second_max_value = max_value;
max_value = vect[i];
}
}
printf("\n\nIl max_value tra i punti importants e':\t%i", max_value);
} */
//find the mean of a given row
int row_mean_value(int mat[][COL], int i, int j) {
int r_mean = 0, sum = 0;
for (int r = i, c = j; c < COL; c++){
sum += mat[r][c];
}
r_mean = sum / COL;
printf("\nrow mean = %i / %i >>> %i", sum, COL, r_mean);
return r_mean;
}
//find the mean value in a given column
int column_mean_value(int mat[][COL], int i, int j) {
int c_mean = 0, sum = 0, r = 0, c = j;
for (r = i; r < ROW; r++){
sum += mat[r][c];
}
c_mean = sum / ROW;
printf("\ncolumn mean = %i / %i >>> %i", sum, ROW, c_mean);
return c_mean;
}
int max_in_vector(int vect[]) {
int max_value = 0, second_max_value = 0;
for (int i = 0; i < ROW*COL; i++) {
if (vect[i] > max_value) {
second_max_value = max_value;
max_value = vect[i];
}
}
return max_value;
}
//search inside the matrix for a given value and communicate its coordinates by modifying pointers to variables
void search_in_matrix(int mat[][COL], int to_search, int *mi, int *mj) {
//row and col variables are used for completeness, else we could just work with pointers
int found = 0, found_row = 0, found_col = 0;
for (int i = 0; i < ROW; i++) {
for (int j = 0; j < COL; j++) {
if (mat[i][j] == to_search) {
found = mat[i][j];
found_col = j;
found_row = i;
}
}
}
*mi = found_row;
*mj = found_col;
return;
}
int Importants(int a[ROW][COL], int *mi, int *mj, int *max){
//init variables, including the ones to modify coordinate pointers
int n_importants = 0, i_coord = 0, j_coord = 0, max_p = 0;
//init mean value variables
int r_mean = 0, c_mean = 0;
//init counters
int i = 0, j = 0, k = 0;
//traversing the matrix
for (i ; i < ROW; i++) {
//calculate the mean of the row we're in
r_mean = row_mean_value(a, i, j);
for (j , k; j < COL; j++, k++) {
//calculating the mean of the column we're in
c_mean = column_mean_value(a, i, j);
//check for Important Point: a[i][j] MUST BE STRICTLY GREATER than r_mean and c_mean
if (a[i][j] > r_mean && a[i][j] > c_mean) {
//increment n_importants counter and fill the supplementary array with the value
n_importants++;
importants_vect[k] = a[i][j];
}
else continue;
}
//reinit j to 0. There are problems in print if not. Still don't know why
j = 0;
}
//search for the max in the supplementary array then search for its coordinates in the matrix
//and pass them back to the coordinate pointers
max_p = max_in_vector(importants_vect);
search_in_matrix(a, max_p, mi, mj);
return n_importants;
}
int main() {
srand(time(NULL));
int mat[ROW][COL];
int mi = 0, mj = 0, max = 0;
create_matrix(mat);
print_matrix(mat);
//zero_vector_init(posizioni);
zero_vector_init(importants_vect);
int n_importants = Importants(mat, &mi, &mj, &max);
//maxi_vect(posizioni);
int max_value = max_in_vector(importants_vect);
//int search = search_in_matrix(mat, max_value);
printf("\n\nThere are %i Important Points inside the matrix", n_importants);
printf("\n\nThe max among Important Points is\t%i\n", max_value);
printf("It's found on the row n°\t%i\n", mi);
printf("And on column n°\t%i\n\n", mj);
//printf("media: %.2f", med);
return 0;
}