Compilare: user.cpp: In function ‘void dijkstra()’: user.cpp:9:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[0].size();i++) ^ user.cpp:11:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<a[0].size();j++) ^ user.cpp:15:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<a[a[0][j].first].size();k++) ^ user.cpp: In function ‘int main()’: user.cpp:45:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<a[0].size();j++) ^ user.cpp:55:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[0].size();i++) ^