Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:28:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a[x].size(); ++i) ^ user.cpp:40:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a[x].size(); ++i) ^ user.cpp: In function ‘void solve(int)’: user.cpp:84:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a[x].size(); ++i) ^ user.cpp:121:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a[start].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:149:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i < st[0].size(); ++i) ^ user.cpp:129:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("symmetricgraph2.in","r",stdin); ^ user.cpp:130:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("symmetricgraph2.out","w",stdout); ^ user.cpp:132:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n,&m); ^ user.cpp:137:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x,&y,&c); ^