Trying to compare chars from matrix C - c

Question

I'm tryingto compare chars from a matrix, but it's not adding any values and i don't know why
so here's my code:
#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>
#define MAX_LINES 1000
#define MAX_LINE_LENGTH 1000
//---------------------
//READING & WRITING
//---------------------
char *ints_new(int n)
{
return (char *) malloc(n * sizeof(char));
}
char **ints2_new(int rows, int cols)
{
char **result = (char **) malloc(rows * sizeof(char *));
char *p = ints_new(rows * cols);
for (int i = 0; i < rows; i++, p += cols)
result[i] = p;
return result;
}
int str_readline(FILE *f, char *s)
{
int result = EOF;
char *p = fgets(s, INT_MAX, f);
if (p != NULL)
{
result = (int) strlen(s);
if (result > 0 && s[result-1] == '\n')
s[--result] = '\0';
}
return result;
}
char *str_dup(const char *s)
{
char *result = (char *) malloc(strlen(s) + 1);
strcpy(result, s);
return result;
}
int strings_read(FILE *f, char **a)
{
int result = 0;
char line[MAX_LINE_LENGTH + 2];
while (str_readline(f, line) != EOF)
a[result++] = str_dup(line);
return result;
}
// --------------------
// Problema A
// --------------------
void values_to_m(char **m, int rows, int cols, char **readings)
{
int i;
int j;
int k = 0;
int l = 0;
for(i = 0; i < rows; i++)
{
for(j = 0; j < cols; j++)
{
m[i][j] = readings[k][l];
l++;
}
k++;
l = 0;
}
}
int count_points(char **m, int i, int j, int rows, int cols)
{
int result = 0;
if(i < rows-2)
{
if(m[i][j] == m[i+1][j] == m[i+2][j])
result++;
if(j < cols-2)
{
if(m[i][j] == m[i][j+1] == m[i][j+2])
result++;
if(m[i][j] == m[i+1][j+1] == m[i+2][j+2])
result++;
}
if(j > 1)
{
if(m[i][j] == m[i+1][j-1] == m[i+2][j-2])
result++;
}
}
else
{
if(j < cols-2)
{
if(m[i][j] == m[i][j+1] == m[i][j+2])
result++;
}
}
printf("%d\n", result);
return result;
}
void points(char **m, int rows, int cols)
{
int i;
int j;
int player1 = 0; //O's
int player2 = 0; //X's
for(i = 0; i < rows; i++)
{
for(j = 0; j < cols; j++)
{
int count;
count = count_points(m, i, j, rows, cols); //counts points
if (m[i][j] == 'X') //if values i'm couning are X, points go to player 2
player2 += count;
else if(m[i][j] == 'O') //if O go to player 1
player1 += count;
}
}
printf("%d %d\n", player1, player2);
}
// --------------------
// --------------------
void test_problem_A()
{
char **readings = malloc((MAX_LINES * MAX_LINE_LENGTH) * sizeof(char) + 1);
int rows = strings_read(stdin, readings); //to read from console
int cols = strlen(readings[0]);
printf("%d\n%d\n", rows, cols); //just to make sure nr of rows and cols is right
char **m = ints2_new(rows, cols); //create matrix
values_to_m(m, rows, cols, readings); //put the values to matrix
points(m, rows, cols); //calculate points
ints2_printf(m, rows, cols, "%c");
}
// --------------------
// --------------------
int main(int argc, char **argv)
{
test_problem_A();
return 0;
}
My programm has to read a bunch of 'X', 'O' and '.'.
If there are 3 'X' in a row(vertical, horizontal or diagonal) player 2 gets 1 point, if the same happens to 'O', player 1 gets 1 point. '.' don't count any points.
my matrix had to have minimum 3 rows and cols and maximum 1000 rows and cols.
example:
If i put in console
XXO
OXO
OXO
player 1 and 2 each get 1 point
if i put:
XXXXXO //(int this line Player 2 get 3 points because there are 3 times 3 X in a row)
OXOXOO
OXOOXO
OXOXOO
player 1 gets 5 points
and player 2 gets 6 points
So my problema is with function "count_points" it's not counting any points, when I print "result" it always gives me 0 points.
Can't I compare 2 chars if they belong in a matrix?
Thanks

Answer 1

In count_points, you try to compare three values with expressions like
if (a == b == c) ...
This doesn't do what you think it does. You treat it like a comparison in mathematical notation, but C interprets it as:
if ((a == b) == c) ...
The comparison a == b yields either 0 or 1. That result is then compared with c.
You could rewrite your desired expression as
if (a == b && b == c) ...
Given that your a, b and c are compound expressions, you could write a small function for that:
static int eq3(int a, int b, int c)
{
return (a == b && b == c);
}
int count_points(char **m, int i, int j, int rows, int cols)
{
int result = 0;
if (i < rows-2) {
if (eq3(m[i][j], m[i+1][j], m[i+2][j]))
result++;
if (j < cols - 2) {
if (eq3(m[i][j], m[i][j+1], m[i][j+2]))
result++;
if (eq3(m[i][j], m[i+1][j+1], m[i+2][j+2]))
result++;
}
if (j > 1) {
if (eq3(m[i][j], m[i+1][j-1], m[i+2][j-2]))
result++;
}
} else {
if (j < cols-2) {
if (eq3(m[i][j], m[i][j+1], m[i][j+2]))
result++;
}
}
return result;
}
As for the allocation of your matrix, see alk's answer. Your method of allocation - one char ** for the rows and then string duplication for the row data, could leave you with a ragged array and you may not safely access m[j + 1][i] for some cases where i is a valid index for row j, but not for row j + 1.

Answer 2

For starters, here you want to allocate pointers to char:
char **readings = malloc((MAX_LINES * MAX_LINE_LENGTH) * sizeof(char) + 1);
So do so:
char **readings = malloc((MAX_LINES * MAX_LINE_LENGTH) * sizeof(char*) + 1);
or even better:
char **readings = malloc((MAX_LINES * MAX_LINE_LENGTH) * sizeof *readings + 1);