Compilare: user.cpp: In function ‘void build(int, int, int)’: user.cpp:25:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < a[b].size() && j < a[c].size()){ ^ user.cpp:25:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < a[b].size() && j < a[c].size()){ ^ user.cpp:35:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; i < a[b].size(); i++){ ^ user.cpp:38:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; j < a[c].size(); j++){ ^ user.cpp: In function ‘int main()’: user.cpp:85:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.cpp:87:47: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d", &v[i].x, &v[i].y); ^ user.cpp:91:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &m); ^ user.cpp:93:56: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d%d%d", &ii1, &jj1, &ii2, &jj2); ^