Compilare: main.cpp: In function 'void dfs(int, int)': main.cpp:15:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < a[x].size(); i++) { ~~^~~~~~~~~~~~~ main.cpp: In function 'void solve()': main.cpp:41:9: warning: unused variable 'i' [-Wunused-variable] int i; ^