Compilare: user.cpp: In function ‘int main()’: user.cpp:21:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<s[i].size();j++) ^ user.cpp:28:113: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][j+1]!='x' && s[i][j+1]!='+' && s[i][j+1]!='-' && s[i][j+1]!='=' && j+1<s[i].size()) ^ user.cpp:39:103: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][j]!='x' && s[i][j]!='+' && s[i][j]!='-' && s[i][j]!='=' && j<s[i].size()) ^ user.cpp:54:103: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][j]!='x' && s[i][j]!='+' && s[i][j]!='-' && s[i][j]!='=' && j<s[i].size()) ^ user.cpp:65:103: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][j]!='x' && s[i][j]!='+' && s[i][j]!='-' && s[i][j]!='=' && j<s[i].size()) ^