Compilare: user.c: In function ‘backtrack_col’: user.c:44:6: warning: unused variable ‘tmp_sum’ [-Wunused-variable] int tmp_sum; ^ user.c: In function ‘backtrack_row’: user.c:63:6: warning: unused variable ‘tmp_sum’ [-Wunused-variable] int tmp_sum; ^ user.c: In function ‘main’: user.c:96:8: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d %d", &n, &m); ^ user.c:104:10: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d", &matrix[i][j]); ^