Compilare: user.cpp: In function ‘void backtracking(int)’: user.cpp:43:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < pList[i].size() && pTaken.find(pList[i][j]) == pTaken.end()) { ^ user.cpp:46:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j == pList[i].size()) { ^ user.cpp:47:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < pList[i].size(); j++) { ^