Compilare: user.c: In function ‘simetric’: user.c:43:9: warning: assignment makes integer from pointer without a cast [enabled by default] s1[2*l]=NULL; s2[2*l]=NULL; ^ user.c:43:23: warning: assignment makes integer from pointer without a cast [enabled by default] s1[2*l]=NULL; s2[2*l]=NULL; ^ user.c: In function ‘back’: user.c:50:5: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (!simetric(level-1,n)) ^ user.c: At top level: user.c:74:6: warning: return type of ‘main’ is not ‘int’ [-Wmain] void main(void) ^ user.c: In function ‘load’: user.c:16:8: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fp,"%d %d",&n,&k); ^