问题描述:

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

网友答案:

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.

网友答案:

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);
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