50125. Consecutive 1’s with Function

#include <stdio.h>
#include "findLength.h"

#define max(a,b) ((a)>(b)?(a):(b))

int is_valid(int x, int y, int n){
    return x >= 0 && y >= 0 && x < n && y < n;
}

int findLength (int arr[][256], int n, int r, int c, int dr, int dc){
    int now_cnt = 0;
    int max_cnt = 0;
    while(is_valid(r, c, n)){
        if(arr[r][c] == 1) now_cnt += 1;
        else now_cnt = 0;
        max_cnt = max(max_cnt, now_cnt);
        r += dr, c += dc;
    }
    return max_cnt;
}