Compilare: main.cpp: In function 'int main()': main.cpp:29:42: warning: NULL used in arithmetic [-Wpointer-arith] if(b[i][j]!='\n' && b[i][j]!=NULL)v[b[i][j]]++; ^~~~ main.cpp:29:56: warning: array subscript has type 'char' [-Wchar-subscripts] if(b[i][j]!='\n' && b[i][j]!=NULL)v[b[i][j]]++; ^ main.cpp:16:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("matrix.in","r",stdin); ^ main.cpp:17:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("matrix.out","w",stdout); ^ main.cpp:19:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ main.cpp:23:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf(" %c",&a[i][j]); ^ main.cpp:28:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf(" %c",&b[i][j]); ^