Compilare: user.cpp: In function ‘void Topological_sort(int)’: user.cpp:52:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < G[x].size(); ++ i) ^ user.cpp: In function ‘void DP(int)’: user.cpp:68:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < G[x].size(); ++ i) ^ user.cpp: In function ‘void Search(int)’: user.cpp:91:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < Prev[x].size(); ++ i) ^ user.cpp: In function ‘void read()’: user.cpp:16:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d\n", &n, &m, &k); ^ user.cpp:19:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%c %c\n", &c1, &c2); ^ user.cpp:3:26: warning: ‘x’ may be used uninitialized in this function [-Wmaybe-uninitialized] #define pb(x) push_back(x) ^ user.cpp:15:9: note: ‘x’ was declared here int x, y; ^