marriage.cpp: In function 'void dfs(int)':
marriage.cpp:44:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
44 | for (i=0;i<g[x].size();++i){
| ~^~~~~~~~~~~~
marriage.cpp: At global scope:
marriage.cpp:52:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
52 | main(){
| ^
marriage.cpp: In function 'int main()':
marriage.cpp:53:13: warning: unused variable 'j' [-Wunused-variable]
53 | int i,k,j;
| ^
marriage.cpp:16:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
16 | #define scan3(a,b,c) scanf("%d %d %d",&a,&b,&c);
| ~~~~~^~~~~~~~~~~~~~~~~~~~~
marriage.cpp:54:5: note: in expansion of macro 'scan3'
54 | scan3(n,m,k)
| ^~~~~
marriage.cpp:15:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
15 | #define scan2(a,b) scanf("%d %d",&a, &b);
| ~~~~~^~~~~~~~~~~~~~~~
marriage.cpp:57:9: note: in expansion of macro 'scan2'
57 | scan2(x,y)
| ^~~~~