Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:52:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int l = 0, k = 1, i = 0, j = 0; i < arr.size(); i = j + 1, j = i, k ++ ) { ^ user.cpp:53:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( j + 1 < arr.size() && std::get<0>(arr[i]) == std::get<0>(arr[j + 1]) ) { ^ user.cpp:57:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( j == arr.size() - 1 ) { ^ user.cpp:63:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int l = 0, k = 1, i = 0, j = 0; i < arr.size(); i = j + 1, j = i, k ++ ) { ^ user.cpp:64:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( j + 1 < arr.size() && std::get<1>(arr[i]) == std::get<1>(arr[j + 1]) ) { ^ user.cpp:68:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( j == arr.size() - 1 ) { ^ user.cpp:88:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, j = 1; i < lst1[p].size() - 1; i = j, j = i + 1 ) { ^ user.cpp:103:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, j = 1; i < lst2[p].size() - 1; i = j, j = i + 1 ) { ^