Compilare: user.cpp: In function ‘std::string compress(std::string)’: user.cpp:25:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < str.length(); i ++ ) { ^ user.cpp:28:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 1; i < str.length(); i ++ ) { ^ user.cpp: In function ‘int main(int, const char**)’: user.cpp:48:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < vec.size(); i ++ ) { ^ user.cpp:50:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( vec[i].length() == k ) { ^ user.cpp:52:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < vec.size(); i ++ ) { ^ user.cpp:54:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j <= str.size(); j ++ ) { ^ user.cpp:56:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( j != str.size() && str[j] == '0' ) continue; ^ user.cpp:63:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < dp[t].size(); j ++ ) { ^ user.cpp:68:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < dp[n % 2].size(); i ++ ) ^